Bed Bug Physiology, Biology, and Behavior

2019

DeVries, Zachary C., Ahmed M. Saveer, Russell Mick, and Coby Schal. 2019. Bed bug (Hemiptera: Cimicidae) attraction to human odors: validation of a two-choice olfactometer. Journal of Medical Entomology 56(2): 362–67. doi: 10.1093/jme/tjy202.

“Bed bugs (Cimex lectularius L.) (Hemiptera: Cimicidae) are obligate hematophagous ectoparasites, and, therefore, must locate suitable hosts to ensure survival and reproduction. Their largely nocturnal activity suggests that chemosensory and thermosensory cues would play critical roles in host location. Yet, the importance of olfaction in host attraction of bed bugs remains unclear. We developed and validated a Y-tube, two-choice olfactometer and tested its suitability for investigating attraction to human odors (from skin swabs). Olfactometer orientation significantly affected the percentage of bed bugs that were activated by human odors, with significantly more bed bugs responding when the olfactometer was oriented vertically (bug introduced at bottom of the olfactometer) compared with all other orientations. Starved (7–10 d) adult males, mated females, and nymphs responded (47–77% moved up the olfactometer and made a choice) when human odors were present in the olfactometer, while starved, unmated females did not respond. Skin swabs from all five human participants elicited high response rates (65–82%), and bed bugs from four different populations responded to skin swabs (40–82% response rate). However, in all assays including those resulting in relatively low response rates, bed bugs exhibited >90% preference for human odors over blank controls. These results provide strong evidence that bed bugs can respond and orient towards human odors, independently of all other host cues. Furthermore, the validated olfactometer should enable rapid and efficient evaluations of bed bug behavioral responses to semiochemicals.”


Kaufmann, Elena, and Oliver Otti. 2019. Males increase their fitness by choosing large females in the common bedbug Cimex lectularius. Animal Biology. 69(1): 17–32. doi: 10.1163/15707563-20181033.

“Mate choice is often a role assigned to females. Already Darwin realised that males are eager to copulate, and females are choosy. However, male mate choice is not as rare as assumed. Males should choose females if females vary in quality, i.e., fecundity. Indeed, males often choose larger mates and through this preference increase fitness benefits. In addition, if mating costs reduce the number of copulations a male can potentially perform, he should be choosy. Bedbug females vary in their fecundity and female size is positively related to fecundity. Male bedbugs are limited in seminal fluid availability and, hence, the number of consecutive matings they can perform. Traumatic insemination gives males full control over mating, therefore low female mating resistance could further allow males to be choosy. Here, using mate choice arenas, we investigated if male bedbugs prefer to mate with large females. We observed mating behaviour and measured female fecundity to investigate potential male fitness benefits. Males chose to mate with large females 1.8 times more often than small females and large females laid significantly more eggs than small females. Our study provides first evidence for male mate choice based on female body size in bedbugs and males can increase their fitness by mating large females. It has to be further established if male mate choice is driven by mating costs in terms of ejaculate investment and if such male mate choice based on female size could be a driver of sexual size dimorphism in bedbugs.”


2018

Basnet, S., and S. T. Kamble2018. Knockdown of the chromatin remodeling gene brahma by RNA interference reduces reproductive fitness and lifespan in common bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. 55(3): 534-539. doi: 10.1093/jme/tjx234

“The common bed bug, Cimex lectularius L. (Hemiptera: Cimicidae) is a nuisance household pest causing significant medical and economic impacts. RNA interference (RNAi) of genes that are involved in vital physiological processes can serve as potential RNAi targets for insect control. Brahma is an ATPase subunit of a chromatin-remodeling complex involved in transcription of several genes for cellular processes, most importantly the homeotic genes. In this study, we used a microinjection technique to deliver double stranded RNA into female bed bugs. Delivery of 0.05 and 0.5 mu g/insect of brahma dsRNA directly into the hemocele resulted in substantial reduction in oviposition. Eggs laid by bed bugs receiving both doses of brahma dsRNA exhibited significantly lower hatching percentage as compared to controls. In addition, brahma RNAi in female bed bugs caused significant mortality. Our results disclosed the potential of brahma RNAi to suppress bed bug population through injection of specific dsRNA, suggesting a critical function of this gene in bed bugs’ reproduction and survival. Based on our data, brahma can be a promising RNAi target for suppression of bed bug population.”


Basnet, S., and S. T. Kamble2018. RNAi-mediated knockdown of vATPase subunits affects survival and reproduction of bed bugs (Hemiptera: Cimicidae). Journal of Medical Entomology. 55(3): 540-546. doi: 10.1093/jme/tjy001

“The common bed bug, Cimex lectularius L. (Hemiptera: Cimicidae) has resurged as one of the most troublesome household pests affecting people across the globe. Bed bug infestations have increased in recent years primarily due to the evolution of insecticide resistance and the insect’s ability to hitchhike with travelers. vATPases are one of the most evolutionarily conserved holoenzymes in eukaryotes, which are mainly involved in proton transport across the plasma membranes and intracellular organelles. RNA interference (RNAi) has been developed as a promising tool for insect control. In this study, we used RNAi as an approach to knock down subunits A and E of the vATPase gene of bed bugs. Delivery of 0.2 µg/insect of dsRNA specific to vATPase-A and vATPase-E into female bed bugs dramatically impaired the laying and viability of eggs over time. Injection of the vATPase-E dsRNA decreased survival of the bed bugs over 30 d. Our results also showed that the knockdown of mRNA is highly effective and persistent up to 30 d post injection. This research demonstrated that silencing of the two vATPase subunits A and E offers a potential strategy to suppress bed bug populations.”


Gershman, S. N., S. A. Harrison, and S. C. Jones. 2018. Opportunities for female choice in the bed bug Cimex lectularius. Ethology 125(2): 92–97. doi: 10.1111/eth.12832

“Bed bugs are cited as exemplars of sexual conflict because mating can only occur via traumatic insemination. However, past antagonistic coevolution between the sexes does not necessarily preclude current female choice. Here, we investigate opportunities for precopulatory female choice in bed bugs. We examined whether females seek out mating opportunities when they gain the most benefit: when females are virgin and/or have recently fed. But, we found that female mating and feeding status had little effect on female attraction to males and male odor. To determine whether females approach male harborages (home crevices) to seek matings in nature, we investigated where matings occurred among unfamiliar pairs of bed bugs. We found that, despite female attraction to male odor, matings were most likely to take place in the female’s harborage rather than the male’s harborage. We also examined the effect of feeding on male and female ability to mate. Whereas previous research reported that engorgement impaired female ability to refuse matings, we found that male feeding status had a larger effect on the success of mating encounters than female feeding status. Fed males had poor mating success, suggesting that males may be faced with a trade‐off between mating and feeding.”


Kim, J. H., C. E. Hwang, K. A. Yoon, K. M. Seong, J. Lee, J. H. Kim, and S. H. Lee. 2018. Molecular and biochemical characterization of the bed bug salivary gland cholinesterase as an acetylcholine-sequestering enzyme. Insect Biochemistry and Molecular Biology. 102: 52–58. doi: 10.1016/j.ibmb.2018.09.009.

“The common bed bug, Cimex lectularius, possesses a cholinesterase expressed exclusively in the salivary gland (ClSChE). In this study, we investigated the molecular forms, tissue distribution patterns and biochemical properties of ClSChE and showed that ClSChE exists as a soluble monomeric form or a soluble dimeric form connected by a disulfide bridge. Immunohistochemical analysis confirmed that ClSChE was expressed in the epithelial cells of both the salivary gland and the duct. In addition, the secretion of monomeric ClSChE through the proboscis during feeding was confirmed by western blotting using a ClSChE-specific antibody. To predict the role of ClSChE injected into the tissue of an animal host, we analyzed the extent of hydrolysis of acetylcholine (ACh) by ClSChE by ultra-performance liquid chromatography-tandem mass spectrometry. ClSChE binding to ACh was not clearly resolved in the binding assay format used in this study, probably due to the weak but detectable ACh-hydrolytic activity of ClSChE. Nevertheless, kinetic analysis revealed that ClSChE possesses extremely low Km (high affinity to ACh) and Vmax values. These findings suggest that ClSChE functions virtually as an ACh-sequestering protein by having a very strong affinity to ACh but an extremely long turnover time. Given that ACh regulates a wide variety of host physiologies, we discuss the tentative roles of ClSChE in blood vessel constriction and itch/pain regulation in the host.”


Predel, R., S. Neupert, C. Derst, K. Reinhardt, and C. Wegener2018. Neuropeptidomics of the bed bug Cimex lectularius. Journal of Proteome Research. 17: 440–454. doi: 10.1021/acs.jproteome.7b00630

“The bed bug Cimex lectularius is a globally distributed human ectoparasite with fascinating biology. It has recently acquired resistance against a broad range of insecticides, causing a worldwide increase in bed bug infestations. The recent annotation of the bed bug genome revealed a full complement of neuropeptide and neuropeptide receptor genes in this species. With regard to the biology of C. lectularius, neuropeptide signaling is especially interesting because it regulates feeding, diuresis, digestion, as well as reproduction and also provides potential new targets for chemical control. To identify which neuropeptides are translated from the genome-predicted genes, we performed a comprehensive peptidomic analysis of the central nervous system of the bed bug. We identified in total 144 different peptides from 29 precursors, of which at least 67 likely present bioactive mature neuropeptides. C. lectularius corazonin and myosuppressin are unique and deviate considerably from the canonical insect consensus sequences. Several identified neuropeptides likely act as hormones, as evidenced by the occurrence of respective mass signals and immunoreactivity in neurohemal structures. Our data provide the most comprehensive peptidome of a Heteropteran species so far and in comparison suggest that a hematophageous life style does not require qualitative adaptations of the insect peptidome.”


2017

Bustamante, J., J. F. Panzarino, T. J. Rupert, and C. Loudon2017. Forces to pierce cuticle of tarsi and material properties determined by nanoindentation: the Achilles’ heel of bed bugs. Biology Open. 6(10): 1541-1551. doi: 10.1242/bio.028381

“The mechanical properties of bed bug (Cimex lectularius L.) tarsi and pretarsi were investigated in order to evaluate their vulnerability to piercing by plant trichomes (sharp microscopic hairs). Nanoindentation was used to measure the force required to insert a sharp probe into the cuticle of these different regions, as well as to determine creep and reduced elastic moduli for the cuticle. Scanning electron microscopy was used to visualize the indents that had been generated by nanoindentation. The force required to insert a cube corner nanoindenter probe into the cuticle was determined for a range of displacements (1 to 9 µm) and strain rates (0.003 to 0.5 s−1). Greater force was required to insert this sharp probe at greater depth or at faster strain rates. A specific region of the pretarsus (membrane with microtrichia), more frequently pierced by trichomes during bed bug locomotion, required approximately 20-30% less force, exhibited more creep, and had a lower reduced elastic modulus for the first micron of indentation, compared to the other regions, although this pattern was not consistent for greater displacements. These mechanical attributes, which will facilitate the initial stage of puncture, in addition to the presence of natural infoldings in the cuticle of this area, may make that area of the pretarsus particularly vulnerable to piercing. This information will help inform development of physical methods for control of insect pests such as bed bugs.”


Campbell, B. E., D. M. Miller, Z. C. Devries, and A. G. Appel2017. Water loss and metabolic activity in bed bug eggs (Cimex lectularius). Physiological Entomology. 42(4): 355-361. doi: 10.1111/phen.12204

“Few studies have evaluated water loss and respiratory activity of insect eggs, particularly insects that are known to live within indoor environments. The present study quantifies water loss and respiratory activity for the eggs of a re-emerging indoor pest of human environments Cimex lectularius (L.). Water loss is measured gravimetrically and calculated as a function of chorion permeability. For these studies, bed bug eggs are placed at 0% relative humidity and repeatedly weighed over 48 h. Temperature effects and bed bug strain differences on the standard metabolic rate (SMR) and respiratory quotient are measured using closed system respirometry. The SMR (V̇O2; mL g−1 h−1) is measured for two field strain bed bugs and compared with a laboratory strain held at one temperature (25 °C). The standard metabolic rate is measured for Harlan (laboratory) strain bed bug eggs at six different temperatures (15, 20, 25, 30, 35 and 39 °C). Total water loss is not significantly different between all three strains. However, water loss across the chorion (chorion permeability) is significantly different between the Harlan laboratory strain and the two field collected strains. Standard metabolic rates for Harlan (laboratory) strain bed bug eggs increase with temperatures from 15 to 35 °C but decline at 39 °C. Overall, the Harlan bed bug eggs have the largest standard metabolic rates (0.18 ± 0.05 mL g−1 h−1) compared with the Epic Center strain eggs (0.14 ± 0.03 mL g−1 h−1) and Richmond strain eggs (0.16 ± 0.04 mL g−1 h−1), although this difference is not significant.”


DeVries, Z., R. Mick, O. Balvín, and C. Schal2017. Aggregation behavior and reproductive compatibility in the family Cimicidae. Scientific Reports. 7. doi: 10.1038/s41598-017-12735-3

“Bed bugs (Cimex lectularius) provide a unique opportunity to understand speciation and host-associated divergence in parasites. Recently, two sympatric but genetically distinct lineages of C. lectularius were identified: one associated with humans and one associated with bats. We investigated two mechanisms that could maintain genetic differentiation in the field: reproductive compatibility (via mating crosses) and aggregation fidelity (via two-choice sheltering assays). Effects were assessed at the intra-lineage level (within human-associated bed bugs), inter-lineage level (between human- and bat-associated bed bugs), and inter-species level (between C. lectularius and Cimex pipistrelli [bat bug]). Contrary to previous reports, bed bugs were found to be reproductively compatible at both the intra- and inter-lineage levels, but not at the inter-species level (although three hybrids were produced, one of which developed into an adult). Lineage- and species-specific aggregation fidelity was only detected in 8% (4 out of 48) of the aggregation fidelity assays run. These results indicate that under laboratory conditions, host-associated lineages of bed bugs are reproductively compatible, and aggregation pheromones are not capable of preventing gene flow between lineages.”


Gries, R., H. Zhai, A. R. Lewis, R. Britton, and G. Gries2017. Common bed bugs can biosynthesize pheromone components from amino acid precursors in human bloodCanadian Journal of Chemistry. 96(2): 212-216. doi: 10.1139/cjc-2017-0407

“We have recently shown that the aggregation pheromone of the common bed bug, Cimex lectularius, comprises a six-component blend of dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), (E)-2-hexenal, (E)-2-octenal, 2-hexanone, and histamine. Here, we tested the hypothesis that bed bugs biosynthesize some pheromone components from amino acid precursors in human blood, namely DMDS and DMTS from L-methionine and histamine from histidine. We tested this hypothesis by (i) allowing bed bugs to feed on and metabolize sheep blood enriched with 13C-labelled histidine or 2H-labelled methionine, (ii) extracting bed bug feces (a source of the aggregation pheromone), and (iii) analyzing feces extracts by GC-MS, HPLC-MS and NMR spectroscopy. The analyses revealed that bed bugs converted 2H-methionine to 2H-DMDS and 2H-DMTS, and 13C-histidine to 13C-histamine. There is not enough histidine in human blood to account for the amount of histamine that bed bugs produce and excrete with their feces, and only a small proportion of the available 13C-histidine was converted to 13C-histamine in our study. Therefore, it is likely that bed bugs biosynthesize histamine, and possibly also DMDS and DMTS, primarily de novo.”


Hinson, K. R., V. Reukov, E. P. Benson, P. A. Zungoli, W. C. Bridges, B. R. Ellis, and J. Song2017. Climbing ability of teneral and sclerotized adult bed bugs and assessment of adhesive properties of the exoskeletal fluid using atomic force microscopy. PLoS One. 12: e0189215. doi: 10.1371/journal.pone.0189215

“We observed that teneral adults (<1 h post-molt) of Cimex lectularius L. appeared more adept at climbing a smooth surface compared to sclerotized adults. Differences in climbing ability on a smooth surface based on sclerotization status were quantified by measuring the height to which bed bugs climbed when confined within a glass vial. The average maximum height climbed by teneral (T) bed bugs (n = 30, height climbed = 4.69 cm) differed significantly (P< 0.01) from recently sclerotized (RS) bed bugs (n = 30, height climbed = 1.73 cm at ~48 h post molt), sclerotized group 1 (S1) bed bugs (n = 30, S1 = 2.42 cm at >72 h), and sclerotized group 2 (S2) bed bugs (n = 30, height climbed = 2.64 cm at >72 h post molt). When heights from all climbing events were summed, teneral bed bugs (650.8 cm climbed) differed significantly (P< 0.01) from recently sclerotized (82 cm climbed) and sclerotized (group 1 = 104.6 cm climbed, group 2 = 107.8 cm climbed) bed bugs. These findings suggested that the external surface of teneral bed bug exoskeletons possess an adhesive property. Using atomic force microscopy (AFM), we found that adhesion force of an exoskeletal (presumably molting) fluid decreased almost five-fold from 88 to 17 nN within an hour of molting. Our findings may have implications for laboratory safety and the effectiveness of bed bug traps, barriers, and biomimetic-based adhesives.”


Hornok, S., S. Krisztina, S. Boldogh, A. Sándor, J. Kontschán, V. Tu, A. Halajian, N. Takács, T. Görföl, and P. Estók2017. Phylogenetic analyses of bat-associated bugs (Hemiptera: Cimicidae: Cimicinae and Cacodminae) indicate two new species close to Cimex lectularius. Parasites & Vectors. 10: 439. doi: 10.1186/s13071-017-2376-1

“Background: Bats are regarded as the primary (ancestral) hosts of bugs of the family Cimicidae. The historically and economically most important species in the family is the common bedbug (Cimex lectularius), because of its worldwide occurrence and association with humans. This molecular-phylogenetic study was initiated in order to expand the knowledge on the phylogeny of cimicid bugs of bats, by investigating samples from Hungary, Romania (representing central-eastern Europe) and two further countries (South Africa and Vietnam). Results: Altogether 216 cimicid bugs were collected (73 Ci. lectularius, 133 Ci. pipistrelli, nine Cacodmus ignotus and one Ca. sparsilis). Members of the Cimex lectularius species group were found both in the environment of bats (only Myotis emarginatus, which is a cave/attic-dwelling species) and on three crevice-dwelling bat species (two pipistrelloid bats and M. bechsteinii). On the other hand, Ci. pipistrelli always occurred off-host (near M. myotis/blythii, which are cave/attic-dwelling species). In addition, two Cacodmus spp. were collected from Pipistrellus hesperidus. The morphological characters of these specimens are illustrated with high resolution pictures. Analysis of cytochrome c oxidase subunit 1 (cox1) sequences generated from 38 samples indicated relative genetic homogeneity of Ci. pipistrelli, while the Ci. lectularius group had two haplotypes (collected from pipistrelloid bats in Hungary and Vietnam) highly divergent from other members of this species group. These results were confirmed with molecular and phylogenetic analyses based on the internal transcribed spacer 2 (ITS2). Bat-associated bugs morphologically identified as Ca. ignotus and Ca. sparsilis were different in their cox1, but identical in their ITS2 sequences. Conclusions: Molecular evidence is provided here on the existence of two new genotypes, most likely new species, within the Ci. lectularius species group. The relevant specimens (unlike the others) were collected from pipistrelloid bats, therefore the association of Ci. lectularius with different bat host species (pipistrelloid vs myotine bats) should be evaluated further as a possible background factor of this genetic divergence. In addition, Ca. ignotus is reported for the first time in South Africa.”


Kim, D.-Y., J. Billen, S. L. Doggett, and C.-Y. Lee2017. Differences in climbing ability of Cimex lectularius and Cimex hemipterus (Hemiptera: Cimicidae). Journal of Economic Entomology. 110: 1179–1186. doi: 10.1093/jee/tox039

“The climbing abilities of two bed bug species, Cimex lectularius L. and Cimex hemipterus (F.), were determined by evaluating their escape rates from smooth surface pitfall traps using four commercial bed bug monitors (Verifi Bed Bug Detector, ClimbUp Insect Interceptor, BlackOut Bed Bug Detector, and SenSci Volcano Bed Bug Detector). All detectors were used in the absence of lures or attractants. Unlike C. lectularius, adult C. hemipterus were able to escape from all traps. On the other hand, no or a low number nymphs of both species escaped, depending on the evaluated traps. Examination of the vertical friction force of adults of both species revealed a higher vertical friction force in C. hemipterus than in C. lectularius. Scanning electron microscope micrograph observation on the tibial pad of adult bed bugs of C. hemipterus showed the presence of a greater number of tenent hairs on the tibial pad than on that of adult C. lectularius. No tibial pad was found on the fourth and fifth instars of both species. Near the base of the hollow tenent hairs is a glandular epithelium that is better developed in adult C. hemipterus than in adult C. lectularius. This study highlights significant morphological differences between C. lectularius and C. hemipterus, which may have implications in the monitoring and management of bed bug infestations.”


Liu, F., Z. Chen, and N. Liu2017. Molecular basis of olfactory chemoreception in the common bed bug, Cimex lectularius. Scientific Reports. 7: 45531. doi: 10.1038/srep45531

“As one of the most notorious ectoparasites, bed bugs rely heavily on human or animal blood sources for survival, mating and reproduction. Chemoreception, mediated by the odorant receptors on the membrane of olfactory sensory neurons, plays a vital role in their host seeking and risk aversion processes. We investigated the responses of odorant receptors to a large spectrum of semiochemicals, including human odorants and plant-released volatiles and found that strong responses were sparse; aldehydes/ketones were the most efficient stimuli, while carboxylic acids and aliphatics/aromatics were comparatively less effective in eliciting responses from bed bug odorant receptors. In bed bugs, both the odorant identity and concentrations play important roles in determining the strength of these responses. The odor space constructed based on the responses from all the odorant receptors tested revealed that odorants within the same chemical group are widely dispersed while odorants from different groups are intermingled, suggesting the complexity of odorant encoding in the bed bug odorant receptors. This study provides a comprehensive picture of the olfactory coding mechanisms of bed bugs that will ultimately contribute to the design and development of novel olfactory-based strategies to reduce both the biting nuisance and disease transmission from bed bugs.”


Liu, F., C. Xiong, and N. Liu2017. Chemoreception to aggregation pheromones in the common bed bug, Cimex lectularius. Insect Biochemistry and Molecular Biology. 82: 62–73. doi: 10.1016/j.ibmb.2017.01.012

“The common bed bug, Cimex lectularius, is an obligate blood-feeding insect that is resurgent worldwide, posing a threat to human beings through its biting nuisance and disease transmission. Bed bug aggregation pheromone is considered a very promising attractant for use in the monitoring and management of bed bugs, but as yet little is known regarding the sensory physiology of bed bugs related to this pheromone. This study examined how the individual components of aggregation pheromone are perceived by the olfactory receptor neurons (ORNs) housed in different types of olfactory sensilla in bed bugs and the molecular basis for the ORNs’ responses to the aggregation pheromone. We found that the ORNs in the D olfactory sensilla played a predominant role in detecting all the components of aggregation pheromone except for histamine, which was only recognized by the C sensilla. Bed bugs’ E sensilla, which include four functionally distinct groups, showed only a very weak but variant sensitivity (both excitatory and inhibitory) to the components of aggregation pheromone. Functional tests of 15 odorant receptors (ORs) in response to the components of aggregation pheromone revealed that most of these components were encoded by multiple ORs with various tuning properties. This study provides a comprehensive understanding of how bed bug aggregation pheromone is perceived and recognized in the peripheral olfactory system and will contribute useful information to support the development of synthetic attractants for bed bug monitoring and control.”


Matos, Y. K., J. A. Osborne, and C. Schal2017. Effects of cyclic feeding and starvation, mating, and sperm condition on egg production and fertility in the common bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. doi: 10.1093/jme/tjx132

“Bed bugs (Cimex lectularius L.) are now endemic in most major cities, but information regarding their basic biology is still largely based on research done over four decades ago. We investigated the effects of starvation, mating, sperm storage, and female and male age on egg production and hatch. Egg production cycles varied with the number of bloodmeals that females received. Once-mated females fed every 5 d had constant egg production for ∼75 d followed by a monotonic decline to near zero. Percentage egg hatch was high and constant, but declined after ∼30 d to near zero. To determine whether the age of the female, male, or sperm affected these patterns, we mated newly eclosed females to 60-d-old virgin males, 60-d-old mated males, or newly eclosed males. Females produced the most eggs when mated to young males, followed by old mated males, and then old virgin males; percentage hatch followed a similar pattern, suggesting that sperm stored within males for long was deficient. To examine effects of sperm stored within females, we mated newly eclosed females, starved them for 30 or 60 d, then fed them every 5 d. The 60-d starved group produced fewer eggs than the 30-d starved group, and both produced fewer eggs than young females mated to old or young males. Longer periods of sperm storage within females caused lower corresponding percentage hatch. These findings indicate egg production and hatch are governed by complex interactions among female and male age, frequency of feeding and mating, and sperm condition.”


Olson, J. F., L. M. V. Vers, R. D. Moon, and S. A. Kells2017. Two compounds in bed bug feces are sufficient to elicit off-host aggregation by bed bugs, Cimex lectularius. Pest Management Science. 73(1): 198–205. doi: 10.1002/ps.4286

“After feeding, bed bugs aggregate in cracks and crevices near a host. Aggregation and arrestment are mediated by tactile and chemical stimuli associated with the bugs’ feces and exuviae. Volatiles derived from fecally stained filter papers were analyzed by solid-phase microextraction (SPME) and evaluated using a multichoice behavioral assay to determine their impact on bed bug aggregation. In addition, crude fecal extracts were collected in methanol, analyzed by gas chromatography coupled with electroantennogram detection (GC-EAD) and mass spectrometry (GC-MS) and evaluated in open-air multichoice behavioral assays. The SPME method was used to detect (E)-2-hexenal and (E)-2-octenal in heated bed bug feces. The presence of these two volatile components did not affect aggregation. Analysis of the crude fecal extracts revealed several semi-volatile nitrogenous compounds, a carboxylic acid and a sulfur-based compound. Adult antennae responded to compounds eluted from three regions of the crude extract using GC-EAD. A combination of two compounds, dimethyl trisulfide and methyldiethanolamine, resulted in aggregation responses equivalent to the original crude extract. Bed bug aggregation is mediated by semi-volatile compounds derived from fecal extracts, and two compounds are sufficient to elicit aggregation. The two compounds identified here could be used to enhance the effectiveness of insecticidal applications or improve monitoring techniques.”


Reinhardt, K., H. G. Breunig, and K. König2017. Autofluorescence lifetime variation in the cuticle of the bedbug Cimex lectularius. Arthropod Structure and Development. 46: 56–62. doi: 10.1016/j.asd.2016.11.009

“The decay time of the fluorescence of excited molecules, called fluorescence lifetime, can provide information about the cuticle composition additionally to widely used spectral characteristics. We compared autofluorescence lifetimes of different cuticle regions in the copulatory organ of females of the bed bug, Cimex lectularius. After two-photon excitation at 720 nm, regions recently characterized as being rich in resilin showed a longer bimodal distribution of the mean autofluorescence lifetime τm (tau-m) at 0.4 ns and 1.0-1.5 ns, while resilin-poor sites exhibited a unimodal pattern with a peak around 0.8 ns. The mean lifetime, and particularly its second component, can be useful to distinguish resilin-rich from resilin-poor parts of the cuticle. The few existing literature data suggest that chitin is unlikely responsible for the main autofluorescent component observed in the resilin-poor areas in our study and that melanin requires further scrutiny. Autofluorescence lifetime measurements can help to characterize properties of the arthropod cuticle, especially when coupled with multiphoton excitation to allow for deeper tissue penetration.”


Rost-Roszkowska, M. M., J. Vilimova, A. Włodarczyk, L. Sonakowska, K. Kamińska, F. Kaszuba, A. Marchewka, and D. Sadílek2017. Investigation of the midgut structure and ultrastructure in Cimex lectularius and Cimex pipistrelli (Hemiptera: Cimicidae). Neotropical Entomology. 46: 45–57. doi: 10.1007/s13744-016-0430-x

“Cimicidae are temporary ectoparasites, which means that they cannot obtain food continuously. Both Cimex species examined here, Cimex lectularius (Linnaeus 1758) and Cimex pipistrelle (Jenyns 1839), can feed on a non-natal host, C. lectularius from humans on bats, C. pipistrellion humans, but never naturally. The midgut of C. lectularius and C. pipistrelli is composed of three distinct regions—the anterior midgut (AMG), which has a sack-like shape, the long tube-shaped middle midgut (MMG), and the posterior midgut (PMG). The different ultrastructures of the AMG, MMG, and PMG in both of the species examined suggest that these regions must fulfill different functions in the digestive system. Ultrastructural analysis showed that the AMG fulfills the role of storing food and synthesizing and secreting enzymes, while the MMG is the main organ for the synthesis of enzymes, secretion, and the storage of the reserve material. Additionally, both regions, the AMG and MMG, are involved in water absorption in the digestive system of both Cimex species. The PMG is the part of the midgut in which spherites accumulate. The results of our studies confirm the suggestion of former authors that the structure of the digestive tract of insects is not attributed solely to diet but to the basic adaptation of an ancestor.”


Seri Masran, S. N. A., and A. H. Ab Majid2017. Genetic diversity and phylogenetic relationships of cytochrome c oxidase subunit I in Cimex hemipterus (Hemiptera: Cimicidae) populations in Malaysia. Journal of Medical Entomology. 54(4): 974-979. doi: 10.1093/jme/tjw227

“The tropical bed bug is scientifically recognized as a significant public health problem. While there is an increased awareness about their resurgence by medical and life science committees, efficient bed bug management still remains unresolved. The solution may soon arise, as information about bed bugs’ infestation dynamics and systematics are becoming more distinguishable. Recent developments in studies about bed bugs are based on molecular intervention by determining their genetic variation and phylogeography. The aim of this study is to assess the phylogenetic relationships and genetic diversity among the populations of tropical bed bugs inhabiting Malaysia. A molecular genotyping study was conducted with 22 tropical bed bug populations composed of three individuals per population. The mitochondrial (COI) gene was used as a marker. The data obtained were analyzed using the T-Coffee, ClustalX, MEGA 6.0, and PAUP software. The results showed one main monophyletic clade that consisted of two groups: Ch01 and Ch02. Ch02 consists of samples from the Bandar Hilir population, differing from the other populations studied by one singleton base. However, as there were no changes in the amino acid, this singleton genetic variation was considered to have no effect on genetic differentiation. Ch01 shows similarity with some sequence of Cimex hemipterus (F.) from Thailand, suggesting an international diversity connection. The disparity index apparently suggests that all isolates are homogeneous populations and are supported by the low value of the mean pairwise distance between isolates. This study will increase the knowledge about phylogeographic diversity of tropical bed bug in Malaysia.”


Talbot, B., O. Balvín, M. Vonhof, H. Broders, B. Fenton, and N. Keyghobadi2017. Host association and selection on salivary protein genes in bed bugs and related blood-feeding ectoparasites. Royal Society Open Science. 4. doi: 10.1098/rsos.170446

“Reciprocal selective pressures can drive coevolutionary changes in parasites and hosts, and result in parasites that are highly specialized to their hosts. Selection and host co-adaptation are better understood in endoparasites than in ectoparasites, whose life cycles may be more loosely linked to that of their hosts. Blood-feeding ectoparasites use salivary proteins to prevent haemostasis in the host, and maximize energy intake. Here we looked for signals of selection in salivary protein genes of ectoparasite species from a single genus (Cimex) that associate with a range of hosts including mammals (bats and humans) and birds (swallows). We analysed two genes that code for salivary proteins that inhibit platelet aggregation and vasoconstriction and may directly affect the efficiency of blood feeding in these species. Significant positive selection was detected at five codons in one gene in all bat-associated species groups. Our results suggest association with bats, versus humans or swallows, has posed a selective pressure on the salivary apyrase gene in species of Cimex.”


Tsujimoto, H., J. M. Sakamoto, and J. L. Rasgon2017. Functional characterization of aquaporin-like genes in the human bed bug Cimex lectularius. Scientific Reports. 7: 3214. doi: 10.1038/s41598-017-03157-2

“The bed bug Cimex lectularius is a blood-feeding re-emerging annoyance pest insect that has the ability to transmit Trypanosoma cruzi under experimental laboratory conditions. Aquaporins (AQPs) are water channel proteins that are essential in biological organisms. Clectularius are constantly exposed to water-related stress, suggesting that AQPs may offer novel control avenues. We identified and cloned four AQPs from Clectularius, assessed tissue and lifestage-specific expression, and characterized biochemical functions in vitro and in vivo. We identified an efficient water-specific AQP (ClAQP1), two aquaglyceroporins (ClGlp1 and ClGlp2) and a homolog of Drosophila melanogaster big brain (ClBib). ClGlp1 was only functional when co-expressed with the water-specific AQP. Simultaneous RNAi gene silencing of ClAQP1 and ClGlp1 significantly reduced water and urea excretion post blood feeding. The Bib homologue was enriched in embryos, exclusively expressed in ovaries, and when silenced, dramatically increased bug fecundity. Our data demonstrate that AQPs have critical roles in excretion, water homeostasis and reproduction in Clectularius, and could be potential targets for control in this notorious pest.”


Wang, Y., R. G. Carballo, and B. Moussian2017. Double cuticle barrier in two global pests, the whitefly Trialeurodes vaporariorum and the bedbug Cimex lectularius. Journal of Experimental Biology. 220: 1396–1399. doi: 10.1242/jeb.156679

“The integument protects the organism against penetration of xenobiotics and water that would potentially interfere with homeostasis. In insects that play key roles in a variety of agricultural and ecological habitats, this inward barrier has barely been investigated. In order to advance knowledge in this field, we studied integumental barrier (cuticle) permeability in the two global pests Trialeurodes vaporariorum (greenhouse whitefly) and Cimex lectularius (bedbug), applying a simple dye-penetration assay. In agreement with our recent findings in Drosophila melanogaster, we show that the surface of these insects is regionalised. We also show that, in contrast to the single barrier in D. melanogaster, two barriers with distinct temperature-sensitive and lipid-based physico-chemical material properties act in parallel to protect these insects against penetration of hydrophilic molecules. These findings imply the existence of unexplored mechanisms by which the cuticle acts as a protective coat against the penetration of water and xenobiotics, including pollutants and insecticides.”


2016

Abd Rahim, A. H., A. H. Ahmad, and A. H. Ab Majid2016. Life table analysis of Cimex hemipterus F. (Hemiptera: Cimicidae) reared on different types of human blood. Asian Pacific Journal of Tropical Disease. 6: 272–277. doi: 10.1016/S2222-1808(15)61030-1

“To determine the development time of each immature stage and total development time of Cimex hemipterus reared on human blood type A, B, O and AB, and to compare survivorship and fecundity of Cimex hemipterus reared on blood type A and AB. Bed bugs were reared on human blood type A, B, O and AB, fed through an artificial feeding system. The number of live and dead individuals, number of nymphs that molted, and number of eggs laid were observed and recorded daily. Statistical analysis showed that no significant difference was observed for the development from egg to adult emergence. Bed bugs reared on blood type A and AB had a life expectancy of 88 and 105 days respectively from the egg stage. The net reproductive rate (R0), mean generation time (T), intrinsic rate of increase (rm), finite rate of increase (λ), and doubling time (DT) for bed bugs reared on blood type A were 12.24, 67.84, 0.037, 1.038 and 18.73, respectively. On the other hand, the same parameters calculated for bed bugs reared on blood type AB produced R0 = 12.58, T = 83.36, rm = 0.030, λ = 1.030 and DT = 23.10. Different blood sources may have different effects on the development time and life characteristics of bed bugs.”


Akhoundi, M., A. Cannet, C. Loubatier, J.-M. Berenger, A. Izri, P. Marty, and P. Delaunay2016. Molecular characterization of Wolbachia infection in bed bugs (Cimex lectularius) collected from several localities in France. Parasite. 23: 31. doi: 10.1051/parasite/2016031

“Wolbachia symbionts are maternally inherited intracellular bacteria that have been detected in numerous insects including bed bugs. The objective of this study, the first epidemiological study in Europe, was to screen Wolbachia infection among Cimex lectularius collected in the field, using PCR targeting the surface protein gene (wsp), and to compare obtained Wolbachia strains with those reported from laboratory colonies of C. lectularius as well as other Wolbachia groups. For this purpose, 284 bed bug specimens were caught and studied from eight different regions of France including the suburbs of Paris, Bouches-du-Rhône, Lot-et-Garonne, and five localities in Alpes-Maritimes. Among the samples, 166 were adults and the remaining 118 were considered nymphs. In all, 47 out of 118 nymphs (40%) and 61 out of 166 adults (37%) were found positive on wsp screening. Among the positive cases, 10 samples were selected randomly for sequencing. The sequences had 100% homology with wsp sequences belonging to the F supergroup strains of Wolbachia. Therefore, we confirm the similarity of Wolbachia strains detected in this epidemiological study to Wolbachia spp. reported from laboratory colonies of C. lectularius.”


Benoit, J. B., et al. 2016. Unique features of a global human ectoparasite identified through sequencing of the bed bug genome. Nature Communications 7: 1–10. doi: 10.1038/ncomms10165

“The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human–bed bug and symbiont–bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite.”


Choe, D.-H., H. Park, C. Vo, and A. Knyshov2016. Chemically mediated arrestment of the bed bug, Cimex lectularius, by volatiles associated with exuviae of conspecifics. PLoS One. 11: e0159520. doi: 10.1371/journal.pone.0159520

“Extracts of the exuviae (cast skins) of nymphal bed bugs (Cimex lectularius) were analyzed for volatile compounds that might contribute to arrestment of adult bed bugs. Four volatile aldehydes, (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal, and 4-oxo-(E)-2-octenal were consistently detected in the headspace of freshly shed exuviae regardless of the developmental stages from which the exuviae were obtained. Quantification of the aldehydes in the solvent extracts of homogenized fresh, 45- or 99-d aged 5th instar exuviae indicated that the aldehydes are present in the exuviae and dissipate over time, through evaporation or degradation. Microscopic observation of the fifth instar exuviae indicated that the dorsal abdominal glands on the exuviae maintained their pocket-like structures with gland reservoirs, within which the aldehydes might be retained. Two-choice olfactometer studies with the volatiles from exuviae or a synthetic blend mimicking the volatiles indicated that adult bed bugs tend to settle close to sources of the aldehydes. Our results imply that the presence and accumulation of bed bug exuviae and the aldehydes volatilizing from the exuviae might mediate bed bugs’ interaction with their microhabitats.”


Christmann, R., H. Auerbach, R. E. Berry, F. A. Walker, and V. Schünemann2016. Nitric oxide heme interactions in nitrophorin from Cimex lectularius. Hyperfine Interactions. 237. doi: 10.1007/s10751-016-1240-6

“The nitrophorin from the bedbug Cimex lectularius (cNP) is a nitric oxide (NO) carrying protein. Like the nitrophorins (rNPs) from the kissing bug Rhodnius prolixus, cNP forms a stable heme Fe(III)-NO complex, where the NO can be stored reversibly for a long period of time. In both cases, the NPs are found in the salivary glands of blood-sucking bugs. The insects use the nitrophorins to transport the NO to the victim’s tissues, resulting in vasodilation and reduced blood coagulation. However, the structure of cNP is significantly different to those of the rNPs from Rhodnius prolixus. Furthermore, the cNP can bind a second NO molecule to the proximal heme cysteine when present at higher concentrations. High field Mössbauer spectroscopy on 57Fe enriched cNP complexed with NO shows reduction of the heme iron and formation of a ferrous nitric oxide (Fe(II)-NO) complex. Density functional theory calculations reproduce the experimental Mössbauer parameters and confirm this observation.”


DeVries, Z. C., S. A. Kells, and A. G. Appel2016. Estimating the critical thermal maximum (CTmax) of bed bugs, Cimex lectularius: comparing thermolimit respirometry with traditional visual methods. Comparative Biochemistry and Physiology Part A, Molecular & Integrative Physiology. 197: 52–57. doi: 10.1016/j.cbpa.2016.03.003

“Evaluating the critical thermal maximum (CTmax) in insects has provided a number of challenges. Visual observations of endpoints (onset of spasms, loss of righting response, etc.) can be difficult to measure consistently, especially with smaller insects. To resolve this problem, Lighton and Turner (2004) developed a new technique: thermolimit respirometry (TLR). TLR combines real time measurements of both metabolism (VCO2) and activity to provide two independent, objective measures of CTmax. However, several questions still remain regarding the precision of TLR and how accurate it is in relation to traditional methods. Therefore, we evaluated CTmax of bed bugs using both traditional (visual) methods and TLR at three important metabolic periods following feeding (1d, 9d, and 21d). Both methods provided similar estimates of CTmax, although traditional methods produced consistently lower values (0.7-1.0°C, [1.26-1.8°F] lower than TLR). Despite similar levels of precision, TLR provided a more complete profile of thermal tolerance, describing changes in metabolism and activity leading up to the CTmax, not available through traditional methods. In addition, feeding status had a significant effect on bed bug CTmax, with bed bugs starved 9d (45.19[±0.20]°C, 113.34[±0.36]°F) having the greatest thermal tolerance, followed by bed bugs starved 1d (44.64[±0.28]°C, 112.35[±0.50]°F), and finally bed bugs starved 21d (44.12[±0.28]°C, 111.42[±0.50]°F). Accuracy of traditional visual methods in relation to TLR is highly dependent on the selected endpoint; however, when performed correctly, both methods provide precise, accurate, and reliable estimations of CTmax.”


DeVries, Z. C., R. Mick, and C. Schal2016. Feel the heat: activation, orientation and feeding responses of bed bugs to targets at different temperatures. Journal of Experimental Biology. 219: 3773–3780. doi: 10.1242/jeb.143487

“Host location in bed bugs is poorly understood. Of the primary host-associated cues known to attract bed bugs – CO2, odors, heat – heat has received little attention as an independent stimulus. We evaluated the effects of target temperatures ranging from 23 to 48°C on bed bug activation, orientation and feeding. Activation and orientation responses were assessed using a heated target in a circular arena. All targets heated above ambient temperature activated bed bugs (initiated movement) and elicited oriented movement toward the target, with higher temperatures generally resulting in faster activation and orientation. The distance over which bed bugs could orient toward a heat source was measured using a 2-choice T-maze assay. Positive thermotaxis was limited to distances <3 cm. Bed bug feeding responses on an artificial feeding system increased with feeder temperature up to 38 and 43°C, and declined precipitously at 48°C. In addition, bed bugs responded to the relative difference between ambient and feeder temperatures. These results highlight the wide range of temperatures that elicit activation, orientation and feeding responses in bed bugs. In contrast, the ability of bed bugs to correctly orient towards a heated target, independently of other cues, is limited to very short distances (<3 cm). Finally, bed bug feeding is shown to be relative to ambient temperature, not an absolute response to feeder blood temperature.”


Gujar, H. and S. R. Palli. 2016. Juvenile hormone regulation of female reproduction in the common bed bug, Cimex lectularius. Scientific Reports. 6: 35546. doi: 10.1038/srep35546.

“To begin studies on reproduction in common bed bug, Cimex lectularius, we identified three genes coding for vitellogenin (Vg, a protein required for the reproductive success of insects) and studied their hormonal regulation. RNA interference studied showed that expression of Vg3 gene in the adult females is a prerequisite for successful completion of embryogenesis in the eggs laid by them. Juvenile hormone (JH) receptor, Methoprene-tolerant (Met), steroid receptor coactivator (SRC) and GATAa but not ecdysone receptor (EcR) or its partner, ultraspiracle (USP) are required for expression of Vg genes. Feeding and mating working through Vg, Met, SRC, EcR, and GATAa regulate oocyte development. Knockdown of the expression of Met, SRC, EcR, USP, BR-C (Broad-Complex), TOR (target of rapamycin), and GATAa in female adults resulted in a reduction in the number eggs laid by them. Interestingly, Kruppel homolog 1 (Kr-h1) knockdown in the adult females did not reduce their fecundity but affected the development of embryos in the eggs laid by females injected with Kr-h1 double-stranded RNA. These data suggest that JH functioning through Met and SRC regulate both vitellogenesis and oogenesis in C. lectularius. However, JH does not work through Kr-h1 but may work through transcription factors not yet identified.”


Gujar, H., and S. R. Palli2016. Krüppel homolog 1 and E93 mediate juvenile hormone regulation of metamorphosis in the common bed bug, Cimex lectularius. Scientific Reports. 6. doi: 10.1038/srep26092

“The common bed bug is an obligate hematophagous parasite of humans. We studied the regulation of molting and metamorphosis in bed bugs with a goal to identify key players involved. qRT-PCR studies on the expression of genes known to be involved in molting and metamorphosis showed high levels of Krüppel homolog 1 [Kr-h1, a transcription factor that plays key roles in juvenile hormone (JH) action] mRNA in the penultimate nymphal stage (N4). However, low levels of Kr-h1 mRNA were detected in the fifth and last nymphal stage (N5). Knockdown of Kr-h1 in N4 resulted in a precocious development of adult structures. Kr-h1 maintains the immature stage by suppressing E93 (early ecdysone response gene) in N4. E93 expression increases during the N5 in the absence of Kr-h1 and promotes the development of adult structures. Knockdown of E93 in N5 results in the formation of supernumerary nymphs. The role of JH in the suppression of adult structures through interaction with Kr-h1 and E93 was also studied by the topical application of JH analog, methoprene, to N5. Methoprene induced Kr-h1 and suppressed E93 and induced formation of the supernumerary nymph. These data show interactions between Kr-h1, E93 and JH in the regulation of metamorphosis in the bed bugs.”


Kaldun, B., and O. Otti2016. Condition-dependent ejaculate production affects male mating behavior in the common bedbug Cimex lectularius. Ecology and Evolution. 6: 2548–2558. doi: 10.1002/ece3.2073

“Food availability in the environment is often low and variable, constraining organisms in their resource allocation to different life-history traits. For example, variation in food availability is likely to induce condition-dependent investment in reproduction. Further, diet has been shown to affect ejaculate size, composition and quality. How these effects translate into male reproductive success or change male mating behavior is still largely unknown. Here, we concentrated on the effect of meal size on ejaculate production, male reproductive success and mating behavior in the common bedbug Cimex lectularius. We analyzed the production of sperm and seminal fluid within three different feeding regimes in six different populations. Males receiving large meals produced significantly more sperm and seminal fluid than males receiving small meals or no meals at all. While such condition-dependent ejaculate production did not affect the number of offspring produced after a single mating, food-restricted males could perform significantly fewer matings than fully fed males. Therefore, in a multiple mating context food-restricted males paid a fitness cost and might have to adjust their mating strategy according to the ejaculate available to them. Our results indicate that meal size has no direct effect on ejaculate quality, but food availability forces a condition-dependent mating rate on males. Environmental variation translating into variation in male reproductive traits reveals that natural selection can interact with sexual selection and shape reproductive traits. As males can modulate their ejaculate size depending on the mating situation, future studies are needed to elucidate whether environmental variation affecting the amount of ejaculate available might induce different mating strategies.”


Kolokotronis, S.-O., J. Foox, J. A. Rosenfeld, M. R. Brugler, D. Reeves, J. B. Benoit, et al2016. The mitogenome of the bed bug Cimex lectularius (Hemiptera: Cimicidae). Mitochondrial DNA Part B. 1: 425–427. doi: 10.1080/23802359.2016.1180268

“We report the extraction of a bed bug mitogenome from high-throughput sequencing projects originally focused on the nuclear genome of Cimex lectularius. The assembled mitogenome has a similar AT nucleotide composition bias found in other insects. Phylogenetic analysis of all protein-coding genes indicates that C. lectularius is clearly a member of a paraphyletic Cimicomorpha clade within the Order Hemiptera.”


Liu, F., and N. Liu2016. Using single sensillum recording to detect olfactory neuron responses of bed bugs to semiochemicals. Journal of Visualized Experiments. 107. doi: 10.3791/53337

“The insect olfactory system plays an important role in detecting semiochemicals in the environment. In particular, the antennal sensilla which house single or multiple neurons inside, are considered to make the major contribution in responding to the chemical stimuli. By directly recording action potential in the olfactory sensillum after exposure to stimuli, single sensillum recording (SSR) technique provides a powerful approach for investigating the neural responses of insects to chemical stimuli. For the bed bug, which is a notorious human parasite, multiple types of olfactory sensillum have been characterized. In this study, we demonstrated neural responses of bed bug olfactory sensilla to two chemical stimuli and the dose-dependent responses to one of them using the SSR method. This approach enables researchers to conduct early screening for individual chemical stimuli on the bed bug olfactory sensilla, which would provide valuable information for the development of new bed bug attractants or repellents and benefits the bed bug control efforts.”


McNeill, C.-A., R.-M. Pereira, P.-G. Koehler, S.-A. McNeill, and R.-W. Baldwin. 2016. Behavioral responses of nymph and adult Cimex lectularius (Hemiptera: Cimicidae) to colored harborages. Journal of Medical Entomology 53(4): 760-769. doi: 10.1093/jme/tjw033

“Behavioral bioassays were conducted to determine whether bed bug adults and nymphs prefer specific colored harborages. Two-choice and seven-choice behavioral color assays indicate that red (28.5%) and black (23.4%) harborages are optimal harborage choices for bed bugs. Yellow and green harborages appear to repel bed bugs. Harborage color preferences change according to gender, nutritional status, aggregation, and life stage. Female bed bugs prefer harborages with shorter wavelengths (lilac—14.5% and violet—11.5%) compared to males, whereas males prefer harborages with longer wavelengths (red—37.5% and black—32%) compared with females. The preference for orange and violet harborages is stronger when bed bugs are fed as opposed to when they are starved. Lone bed bugs (30%) prefer to be in black harborages while red harborages appear to be the optimum harborage color for bed bugs in more natural mixed aggregations (35.5%). Bed bug nymphs preferred different colored harborages at each stage of development, which is indicative of their developing eye structures and pigments. First instars showed no significant preference for any colored harborage soon after hatching. However, by the fifth instar, 27.5% of nymphs significantly preferred red and black harborages (which was a similar preference to adult bed bugs). The proportion of oviposited eggs was significantly greater under blue, red, and black harborages compared to other colored harborages tested. The use of visual cues such as specific colors offers great potential for improving bed bug monitoring tools by increasing trap captures.”


McNeill, C. A., S. A. Allan, P. G. Koehler, R. M. Pereira, and E. N. I. Weeks2016. Vision in the common bed bug Cimex lectularius L. (Hemiptera: Cimicidae): Eye morphology and spectral sensitivity. Medical and Veterinary Entomology. 30: 426–434. doi: 10.1111/mve.12195

“Bed bugs as pests of public health importance recently experienced a resurgence in populations throughout the U.S. and other countries. Consequently, recent research efforts have focused on improving understanding of bed bug physiology and behaviour to improve management. While few studies have investigated the visual capabilities of bed bugs, the present study focused specifically on eye morphology and spectral sensitivity. A 3-D imaging technique was used to document bed bug eye morphology from the first instar through adult and revealed morphological characteristics that differentiate the common bed bug from the tropical bed bug as well as sex-specific differences. Electrophysiological measurements were used to evaluate the spectral sensitivity of adult bed bugs. Male bed bugs were more responsive than females at some wavelengths. Electrophysiological studies provided evidence for at least one photoreceptor with a spectral sensitivity curve peak in the green (λmax 520 nm) region of the spectrum. The broadened long wavelength portion of the spectral sensitivity curve may potentially indicate another photoreceptor in the yellow–green (λmax 550 nm) portion of the spectrum or screening pigments. Understanding more about bed bug visual biology is vital for designing traps, which are an important component of integrated bed bug management.”


Moriyama, M., T. Hosokawa, M. Tanahashi, N. Nikoh, and T. Fukatsu2016. Suppression of bedbug’s reproduction by RNA interference of vitellogenin. PLoS One. 11: e0153984. doi: 10.1371/journal.pone.0153984

“Recent resurgence of the bedbug Cimex lectularius is a global problem on the public health. On account of the worldwide rise of insecticide-resistant bedbug populations, exploration of new approaches to the bedbug control and management is anticipated. In this context, gene silencing by RNA interference (RNAi) has been considered for its potential application to pest control and management, because RNAi enables specific suppression of target genes and thus flexible selection of target traits to be disrupted. In this study, in an attempt to develop a control strategy targeting reproduction of the bedbug, we investigated RNAi-mediated gene silencing of vitellogenin (Vg), a major yolk protein precursor essential for oogenesis. From the bedbug transcriptomes, we identified a typical Vg gene and a truncated Vg gene, which were designated as ClVg and ClVg-like, respectively. ClVg gene was highly expressed mainly in the fat body of adult females, which was more than 100 times higher than the expression level of ClVg-like gene, indicating that ClVg gene is the primary functional Vg gene in the bedbug. RNAi-mediated suppression of ClVg gene expression in adult females resulted in drastically reduced egg production, atrophied ovaries, and inflated abdomen due to hypertrophied fat bodies. These phenotypic consequences are expected not only to suppress the bedbug reproduction directly but also to deteriorate its feeding and survival indirectly via behavioral modifications. These results suggest the potential of ClVg gene as a promising target for RNAi-based population management of the bedbug.”


Sadílek, D., R. B. Angus, F. Šťáhlavský, and J. Vilímová2016. Comparison of different cytogenetic methods and tissue suitability for the study of chromosomes in Cimex lectularius (Heteroptera, Cimicidae). Comparative Cytogenetics. 10: 731–752. doi: 10.3897/CompCytogen.v10i4.10681

“In the article we summarize the most common recent cytogenetic methods used in analysis of karyotypes in Heteroptera. We seek to show the pros and cons of the spreading method compared with the traditional squashing method. We discuss the suitability of gonad, midgut and embryo tissue in Cimex lectularius Linnaeus, 1758 chromosome research and production of figures of whole mitosis and meiosis, using the spreading method. The hotplate spreading technique has many advantages in comparison with the squashing technique. Chromosomal slides prepared from the testes tissue gave the best results, tissues of eggs and midgut epithelium are not suitable. Metaphase II is the only division phase in which sex chromosomes can be clearly distinguished. Chromosome number determination is easy during metaphase I and metaphase II. Spreading of gonad tissue is a suitable method for the cytogenetic analysis of holokinetic chromosomes of Cimex lectularius.”


Ulrich, K. R., M. Kramer, and M. F. Feldlaufer2016. Ability of bed bug (Hemiptera: Cimicidae) defensive secretions (E)-2-hexenal and (E)-2-octenal to attract adults of the common bed bug Cimex lectularius: Defensive secretions attract bed bugs. Physiological Entomology. 41: 103–110. doi: 10.1111/phen.12129

“Accurate and timely surveillance of bed bug infestations is critical for the development of effective control strategies. Although the bed bug-produced volatiles (E)-2-hexenal and (E)-2-octenal are considered as defensive secretions, the present study demonstrates, using ETHOVISION® video-tracking software (Noldus Information Technology Inc., Leesburg, Virginia), that low amounts of these commercially-obtained aldehydes function as attractants, and high amounts function as local repellents, against the common bed bug Cimex lectularius L. In behavioural assays, both males and female C. lectularius are attracted to 0.04 µg of an aldehyde blend (1 : 1) for up to 1 h after initial treatment of filter paper disks. Males differ from females in their response to higher amounts of aldehydes, with females and males exhibiting maximum local repellency at 40 µg and 400 µg, respectively. The results suggest that these bed bug secretions may be candidates for lures and monitors.”


Wang, D., C. Wang, N. Singh, R. Cooper, C. Zha, and A. L. Eiden2016. Effect of mating status and age on the male mate choice and mating competency in the common bed bug, Cimex lectularius (Hemiptera: Cimicidae). Journal of Economic Entomology. 109: 1333–1340. doi: 10.1093/jee/tow077

“We investigated male mate choice and mating competency in the common bed bug, Cimex lectularius L., using video tracking for 10 min per experiment. In the male mate choice experiment, when a male was placed with two females of different mating status, males preferred to initiate copulation with the virgin female more quickly than with the mated female, and the mean total copulation duration with virgin females (38.0 ± 3.0 s) was significantly longer than with mated females (14.6 ± 3.0 s). When a male was placed with two females of different age, males initiated copulation more quickly with the old virgin female (29–34 d adult emergence) than with the young virgin one (<7 d adult emergence), and the mean total copulation duration with old virgin females (38.4 ± 4.0 s) was significantly longer than with young virgin females (24.0 ± 3.0 s). In the male mating competency experiment where a female was placed with two males of different mating status or age, the virgin males were more eager to mate than the mated males, and the old virgin males (29–34 d adult emergence) were more eager than the young virgin males (<7 d adult emergence), with eagerness measured by the percentage of first mate selected (first copulation occurred) and the total copulation duration by each group of males. Male mating competency is related to postmating duration (PMD); males mated 1 d earlier were significantly less likely to mate than virgin males. However, males mated 7 d earlier showed no significant difference in mating competency compared to virgin males. In conclusion, mate choice in C. lectularius is associated with both male and female mating status, age, and PMD.”


2015

Baker, G. T., A. Lawrence, R. Kuklinski, and J. Goddard2015. Post-embryonic development of the compound eye of bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae). Proceedings of the Entomological Society of Washington. 117: 1–6. doi: 10.4289/0013-8797.117.1.1

“Nymphs and adults of the bed bug, Cimex lectularius L,. have compound eyes located on protrusions from the lateral area of the head. In this study, nine specimens from each nymphal instar, and ten adult males and females were examined by scanning electron microscopy to count and measure the ommatidia through the various developmental stages. Ommatidia making up the nymphal and adult eye were found to be round-to-oval and strongly convex. Numbers of ommatidia in the compound eye differed significantly between each nymphal instar and adults of both sexes; however, there was no significant difference in number of ommatidia between females and males. Ommatidial diameter in the first three instars ranged from 24.10 mm to 28.55 mm, whereas this range was much greater in later instars and adults, 20.35 mm – 30.15 mm. Diameters of the largest ommatidia ranged from 29.80 mm to 30.15 mm, and this size range was found on all nymphal instars and adults. The surface of the ommatidia was found to be smooth and without inter-ommatidial setae. The 6.5x increase in number of ommatidia from nymphal instar one to the adult stage is distinctly less than that found in other members of the Hemiptera. A linear relationship exists between width of the pronotum and number of ommatidia found in each nymphal instar and adults.”


DeVries, Z. C., S. A. Kells, and A. G. Appel. 2015. Effects of starvation and molting on the metabolic rate of the bed bug (Cimex lectularius L.). Physiological and Biochemical Zoology. 88(1):53-65. doi: 10.1086/679499

“The bed bug (Cimex lectularius L.) is a common hematophagous pest in the urban environment and is capable of surviving extended periods of starvation. However, the relationship between starvation and metabolism in bed bugs is not well understood. To better understand this relationship, we measured the metabolism of all life stages for >900 h after feeding (starvation) using closed-system respirometry. Measurements were made around molting for the immature life stages, which occurs only after a blood meal. In addition, both mated and unmated adults were measured. Starvation and molting had significant effects on the metabolism of the bed bug. Mass-specific metabolic rate (V(O2); mL g(-1) h(-1)) declined in a curvilinear fashion with the period of starvation for adults and with the postmolting period for immature bed bugs (used to standardize all immature life stages). A standard curve was developed to depict the generalized pattern of metabolic decline observed in all life stages that molted. Individual metabolic comparisons among life stages that molted revealed some differences in metabolic rate between unmated males and females. In addition, the mass scaling coefficient was found to decline with starvation time (postmolting time) for all life stages that molted. In most life stages, the ratio of V(CO2) to V(O2) (respiratory exchange ratio) declined over time, indicating a change in metabolic substrate with starvation. Finally, daily percent loss in body mass declined in a pattern similar to that of V(O2). The observed patterns in metabolic decline are evaluated in relation to the life history of bed bugs. In addition, the evolutionary development of these patterns is discussed. The metabolic pattern after feeding was also found to share several similarities with that of other ectothermic species.”


Gries, R., R. Britton, M. Holmes, H. Zhai, J. Draper, and G. Gries2015. Bed bug aggregation pheromone finally identified. Angewandte Chemie International Edition. 54: 1135–1138. doi: 10.1002/anie.201409890

“Bed bugs have become a global epidemic and current detection tools are poorly suited for routine surveillance. Despite intense research on bed bug aggregation behavior and the aggregation pheromone, which could be used as a chemical lure, the complete composition of this pheromone has thus far proven elusive. Here, we report that the bed bug aggregation pheromone comprises five volatile components (dimethyl disulfide, dimethyl trisulfide, (E)‐2‐hexenal, (E)‐2‐octenal, 2‐hexanone), which attract bed bugs to safe shelters, and one less‐volatile component (histamine), which causes their arrestment upon contact. In infested premises, a blend of all six components is highly effective at luring bed bugs into traps. The trapping of juvenile and adult bed bugs, with or without recent blood meals, provides strong evidence that this unique pheromone bait could become an effective and inexpensive tool for bed bug detection and potentially their control.”


Hottel B. A., R. M. Pereira, S. A. Gezan, R. Qing R, W. M. Sigmund, and P. G. Koehler. 2015. Climbing ability of the common bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. 52(3): 289-295. doi: 10.1093/jme/tjv012

“Little is known about what factors influence the climbing ability of bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), in relation to the various surfaces they encounter. We examined how sex, time since last fed, and what surfaces the bed bugs were in contact with affected their climbing performance. The effects of sex and time since fed were tested by counting the number of bed bugs able to climb a 45° slope. The pulling force was recorded using an analytical balance technique that captured the sequential vertical pulling force output of bed bugs attached to various surfaces. Recently fed female bed bugs were found to have the most difficulty in climbing smooth surfaces in comparison with males. This difference can be explained by the larger weight gained from bloodmeals by female bed bugs. A variety of vertical pulling forces were observed on surfaces ranging from sandpaper to talc powder-covered glass. For surfaces not treated with talc powder, bed bugs generated the least amount of vertical pulling force from synthetically created 0.6-µm plastron surfaces. This vast range in the ability of bed bugs to grip onto various surfaces may have implications on limiting bed bugs dispersal and hitchhiking behaviors.”


Liu, F., and N. Liu. 2015. Human odorant reception in the common bed bug, Cimex lectularius. Scientific Reports. 5: 15558. doi: 10.1038/srep15558

“The common bed bug Cimex lectularius is a temporary ectoparasite on humans and currently resurgent in many developed countries. The ability of bed bugs to detect human odorants in the environment is critical for their host-seeking behavior. This study deciphered the chemical basis of host detection by investigating the neuronal response of olfactory sensilla to 104 human odorants using single sensillum recording and characterized the electro-physiological responses of bed bug odorant receptors to human odorants with the Xenopus expression system. The results showed that the D type of olfactory sensilla play a predominant role in detecting the human odorants tested. Different human odorants elicited different neuronal responses with different firing frequencies and temporal dynamics. Particularly, aldehydes and alcohols are the most effective stimuli in triggering strong response while none of the carboxylic acids showed a strong stimulation. Functional characterization of two bed bug odorant receptors and co-receptors in response to human odorants revealed their specific responses to the aldehyde human odorants. Taken together, the findings of this study not only provide exciting new insights into the human odorant detection of bed bugs, but also offer valuable information for developing new reagents (attractants or repellents) for the bed bug control.”


Narain, R. B., H. Wang, and S. T. Kamble2015. Differential gene expression profiling in bed bug (Cimex lectularius L.) fed on Ibuprofen and caffeine in reconstituted human blood. Entomology, Ornithology & Herpetology: Current Research. 1–12. doi: 10.4172/2161-0983.1000160

“The recent resurgence of the common bed bug (Cimex lectularius L.) infestations worldwide has created a need for renewed research on biology, behavior, population genetics and management practices. Humans serve as exclusive hosts to bed bugs in urban environments. Since a majority of humans consume Ibuprofen (as pain medication) and caffeine (in coffee and other soft drinks) so bug bugs subsequently acquire Ibuprofen and caffeine through blood feeding. However, the effect of these chemicals at genetic level in bed bug is unknown. Therefore, this research was conducted to determine differential gene expression in bed bugs using RNA-Seq analysis at dosages of 200 ppm Ibuprofen and 40 ppm caffeine incorporated into reconstituted human blood and compared against the control. Total RNA was extracted from a single bed bug per replication per treatment and sequenced. Read counts obtained were analyzed using Bioconductor software programs to identify differentially expressed genes, which were then searched against the non-redundant (nr) protein database of National Center for Biotechnology Information (NCBI). Data on comparison of differentially expressed genes between control and Ibuprofen treatments revealed that 659 genes were significantly differentially regulated and 95% of them returned BLAST hits. Heat stress proteins were among the top significantly differentially down regulated genes. Comparison of the control vs caffeine treatments revealed that 2,161 genes were significantly differently regulated (Padj <0.05). Heat shock proteins were among the top ten down regulated genes in both treatments. Finally, using RNAi to identify the exact function of these highly differentially expressed genes and regulating these genes may offer potential for managing bed bug populations.”


Raffaele, J., B. McCarthy, R. W. Raab, and R. Vaidyanathan2015. Autosomal short tandem repeats and an Alu insertion polymorphism are detectable in Cimex lectularius L. (Hemiptera: Cimicidae) for 48 hours after human blood ingestion. Journal of Agricultural and Urban Entomology. 31: 62–69. doi: 10.3954/JAUE15-03.1

“Human DNA has been identified successfully from several hematophagous and necrophagous insects. Because bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), imbibe human blood and achieve high population densities in human habitations, we assessed the stability of human DNA in bed bugs over time and matched blood isolated from bed bugs to an individual human host. Using polymorphic autosomal short tandem repeat (STR) markers commonly employed in forensic investigations and an alu insertion polymorphism, we unambiguously identified human DNA in bed bugs up to 48 h after blood ingestion and visualized faint bands from bed bugs fed 72 h prior. Using STR markers, we could not identify human DNA in bed bug excreta at any time point after blood ingestion. All blood samples matched identical STRs amplified from the host that the bed bugs had fed on, indicating the feasibility of this approach to identify a human host within 48–72 h of blood ingestion.”


Singh, N., C. Wang, and R. Cooper. 2015. Role of vision and mechanoreception in bed bug, Cimex lectularius L. behavior. PLoS One. 10(3): e0118855. doi: 10.1371/journal.pone.0118855

“The role of olfactory cues such as carbon dioxide, pheromones, and kairomones in bed bug, Cimex lectularius L. behavior has been demonstrated. However, the role of vision and mechanoreception in bed bug behavior is poorly understood. We investigated bed bug vision by determining their responses to different colors, vertical objects, and their ability to detect colors and vertical objects under low and complete dark conditions. Results show black and red paper harborages are preferred compared to yellow, green, blue, and white harborages. A bed bug trapping device with a black or red exterior surface was significantly more attractive to bed bugs than that with a white exterior surface. Bed bugs exhibited strong orientation behavior toward vertical objects. The height (15 vs. 30 cm tall) and color (brown vs. black) of the vertical object had no significant effect on orientation behavior of bed bugs. Bed bugs could differentiate color and detect vertical objects at very low background light conditions, but not in complete darkness. Bed bug preference to different substrate textures (mechanoreception) was also explored. Bed bugs preferred dyed tape compared to painted tape, textured painted plastic, and felt. These results revealed that substrate color, presence of vertical objects, and substrate texture affect host-seeking and harborage-searching behavior of bed bugs. Bed bugs may use a combination of vision, mechanoreception, and chemoreception to locate hosts and seek harborages.”


Ulrich, K. R., M. F. Feldlaufer, M. Kramer, and R. J. St. Leger2015. Inhibition of the entomopathogenic fungus Metarhizium anisopliae sensu lato in vitro by the bed bug defensive secretions (E)-2-hexenal and (E)-2-octenal. BioControl. 60: 517–526. doi: 10.1007/s10526-015-9667-2

“The two major aldehydes (E)-2-hexenal and (E)-2-octenal emitted as defensive secretions by bed bugs Cimex lectularius L. (Hemiptera: Cimicidae), inhibit the in vitro growth of an isolate of Metarhizium anisopliae sensu lato (s.l.) (Metsch.) Sokorin (Hypocreales: Clavicipitaceae) (ARSEF 1548). These chemicals inhibit fungal growth by direct contact and via indirect exposure (“fumigation”). Fumigation with (E)-2-octenal for as little as 0.5 h was sufficient to inhibit all fungal growth. Bed bugs placed on filter paper treated with an isolate of M. anisopliae s.l. conidia in the absence of (E)-2-octenal exhibited 99 % mortality after one week. However, bed bugs placed on fungal-treated filter paper and exposed to (E)-2-octenal at 1 h experienced 10 % mortality. The inhibition of fungal growth by bed bug aldehydes is discussed in the context of other biotic and abiotic barriers to infection.”


Wawrocka, K., O. Balvín, and T. Bartonička. 2015. Reproduction barrier between two lineages of bed bug (Cimex lectularius) (Heteroptera: Cimicidae). Parasitology Research. 114: 3019-3025. doi: 10.1007/s00436-015-4504-1

“Populations of bed bugs, Cimex lectularius, have increased in recent years spreading into numerous urban areas across the Western world and making them an increasingly important pest of the twenty-first century. Research into hybridization within and between different lineages of bed bugs can help us to understand processes of micro- and macroevolution in these ectoparasites and may inform the control of this pest species. Hybridization experiments between two host lineages of bed bug (C. lectularius) from Central Europe (Czech Republic), those associated with humans and those with bats, were conducted under laboratory conditions. Number of eggs and early instars were compared between crosses of mixed host lineages (interspecific mating) with pairs from the same host lineage, those from the same locality and same lineage from different localities (intraspecific mating). While crosses within host lineages resulted in egg production and later instars, crosses between different host lineages were unsuccessful, although of the mated females possessed sperm in their mesospermaleges and/or seminal conceptacles. These crosses did not even result in egg production. Moreover, in the mixed lineage crosses, mortality rates in adults were higher (51 and 50 % higher in bat and human lineage, respectively) than in those animals from the same lineage. Survival of adults was in pairs from the same locality slightly higher than in pairs from different localities and differed statistically. These results support the existence of postmating barriers and show reproductive isolation between two lineages of C. lectularius. Bat and human host adaptations can promote evolving of such barriers and can be product of alloxenic speciation.”


2014

Aak, A., B. A. Rukke, A. Soleng, and M. K. Rosnes. 2014. Questing activity in bed bug populations: male and female responses to host signals. Physiological Entomology. 39(3): 199-207. doi: 10.1111/phen.12062

Sex differences in bed bug behavioral responses to a stimulus (human host or carbon dioxide gas) were observed. Compared to males, female bed bugs responded more strongly to the human host signal, were more active while acclimating to a new environment, had quicker responses after feeding, and remained exposed for longer periods of time during the day.


Hansen, I. A., S. D. Rodriguez, L. L. Drake, D. P. Price, B. N. Blakely, J. I. Hammond, H. Tsujimoto, E. Y. Monroy, W. A. Maio, and A. Romero. 2014. The odorant receptor co-receptor from the bed bug, Cimex lectularius L. PLoS One. 10(3): e0119059. doi:10.1371/journal.pone.0119059

“Recently, the bed bug, Cimex lectularius L. has re-emerged as a serious and growing problem in many parts of the world. Presence of resistant bed bugs and the difficulty to eliminate them has renewed interest in alternative control tactics. Similar to other haematophagous arthropods, bed bugs rely on their olfactory system to detect semiochemicals in the environment. Previous studies have morphologically characterized olfactory organs of bed bugs’ antenna and have physiologically evaluated the responses of olfactory receptor neurons (ORNs) to host-derived chemicals. To date, odorant binding proteins (OBPs) and odorant receptors (ORs) associated with these olfaction processes have not been studied in bed bugs. Chemoreception in insects requires formation of heteromeric complexes of ORs and a universal OR coreceptor (Orco). Orco is the constant chain of every odorant receptor in insects and is critical for insect olfaction but does not directly bind to odorants. Orco agonists and antagonists have been suggested as high-value targets for the development of novel insect repellents. In this study, we have performed RNAseq of bed bug sensory organs and identified several odorant receptors as well as Orco. We characterized Orco expression and investigated the effect of chemicals targeting Orco on bed bug behavior and reproduction. We have identified partial cDNAs of six C. lectularius OBPs and 16 ORs. Full length bed bug Orco was cloned and sequenced. Orco is widely expressed in different parts of the bed bug including OR neurons and spermatozoa. Treatment of bed bugs with the agonist VUAA1 changed bed bug pheromone-induced aggregation behavior and inactivated spermatozoa. We have described and characterized for the first time OBPs, ORs and Orco in bed bugs. Given the importance of these molecules in chemoreception of this insect they are interesting targets for the development of novel insect behavior modifiers.”


Hwang, C. E., Y. H. Kim, D. H. Kwon, K. M. Seong, J. Y. Choi, Y. H. Je, and S. H. Lee. 2014. Biochemical and toxicological properties of two acetylcholinesterases from the common bed bug, Cimex lectularius. Pesticide Biochemistry Physiology. 110: 20–26. doi: 10.1016/j.pestbp.2014.02.002

“We examined the molecular and enzymatic properties of two acetylcholinesterases (AChEs; ClAChE1 and ClAChE2) from the common bed bug, Cimex lectularius. Native polyacrylamide gel electrophoresis followed by activity staining and Western blotting revealed that ClAChE1 is the main catalytic enzyme and is abundantly expressed in various tissues. Both ClAChEs existed in dimeric form connected by a disulfide bridge and were attached to the membrane via a glycophosphatidylinositol anchor. To determine their kinetic and inhibitory properties, both ClAChE1 and ClAChE2 were in vitro expressed in Sf9 cells using a baculovirus expression system. ClAChE1 showed higher catalytic efficiency toward acetylcholine, supporting the hypothesis that ClAChE1 plays a major role in postsynaptic transmission. An inhibition assay revealed that ClAChE1 is generally more sensitive to organophosphates and carbamates examined although ClAChE2 was >4000-fold more sensitive to malaoxon than ClAChE1. The relatively higher correlation between the in vitro ClAChE1 inhibition and the in vivo toxicity suggested that ClAChE1 is the more relevant toxicological target for organophosphates and carbamates. Although the physiological function of ClAChE2 remains to be elucidated, ClAChE2 also appears to have neuronal functions, as judged by its tissue distribution and molecular and kinetic properties. Our findings help expand our knowledge on insect AChEs and their toxicological properties.”


Kamimura, Y., H. Mitsumoto, and C.-Y. Lee. 2014. Duplicated female receptacle organs for traumatic insemination in the tropical bed bug Cimex hemipterus: adaptive variation or malformation? PLoS One. 9(2): e89265. doi: 10.1371/journal.pone.0089265

In Cimex hemipterus and C. lectularius, females normally possess a single spermalege on the right side of the abdomen. Female aberrant morphs of C. hemipterus with two spermaleges were studied. Results showed that under laboratory conditions, the spermaleges on both sides were competent. However, the female remained unfertilized when the right-side spermalege (the normal insemination site) was covered up during mating, apparently due to handedness in male mating behavior.


Liu, F., K. F. Haynes, A. G. Appel, and N. Liu. 2014. Antennal olfactory sensilla responses to insect chemical repellents in the common bed bug, Cimex lectularius. Journal of Chemical Ecology. 40: 522–533. doi: 10.1007/s10886-014-0435-z

“Populations of the common bed bug Cimex lectularius (Hemiptera; Cimicidae), a temporary ectoparasite on both humans and animals, have surged in many developed countries. Similar to other haematophagous arthropods, C. lectularius relies on its olfactory system to detect semiochemicals in the environment, including both attractants and repellents. To elucidate the olfactory responses of the common bed bug to commonly used insect chemical repellents, particularly haematophagous repellents, we investigated the neuronal responses of individual olfactory sensilla in C. lectularius’ antennae to 52 insect chemical repellents, both synthetic and botanic. Different types of sensilla displayed highly distinctive response profiles. While C sensilla did not respond to any of the insect chemical repellents, Dγ sensilla proved to be the most sensitive in response to terpene-derived insect chemical repellents. Different chemical repellents elicited neuronal responses with differing temporal characteristics, and the responses of the olfactory sensilla to the insect chemical repellents were dose-dependent, with an olfactory response to the terpene-derived chemical repellent, but not to the non-terpene-derived chemical repellents. Overall, this study furnishes a comprehensive map of the olfactory response of bed bugs to commonly used insect chemical repellents, providing useful information for those developing new agents (attractants or repellents) for bed bug control.”


Olson, J. F., R. D. Moon, S. A. Kells, and K. A. Mesce. 2014. Morphology, ultrastructure and functional role of antennal sensilla in off-host aggregation by the bed bug, Cimex lectularius. Arthropod Structure Development. 43: 117–122. doi: 10.1016/j.asd.2013.12.004

“After blood feeding on a host, bed bugs, Cimex lectularius, assemble in aggregation sites away from the host. Off-host aggregation is mediated by a combination of mechanical and chemical stimuli associated with bug feces. Partial antennectomies indicated removal of flagellomeres did not affect aggregation, but removal of the whole pedicel or its distal half significantly reduced (P < 0.01) aggregation, suggesting that sensilla related to off-host aggregation occur on the distal half of the pedicel. Scanning electron microscopy (SEM) revealed that serrated hairs were distributed throughout the pedicel, but newly described smooth hairs were present mainly on the distal half, and a distinct patch of grooved pegs, smooth pegsand immersed cones was present on the posterior edge of the distal half of the pedicel in adults, but not in nymphs. Numbers of different types of sensilla increased significantly during metamorphosis from first instar to adult (P < 0.05), but were similar between genders (P = 0.11) and between females from a laboratory and field strain of bugs (P = 0.19). Transmission electron microscopy (TEM) revealed that cuticular pores were present in the two types of pegs, indicating that the pegs have an olfactory function. The smooth hairs resembled gustatory sensilla previously described in Cimex hemipterus F. The existence of both olfactory and gustatory sensilla on the distal half of the pedicel suggests those sensilla may be the sensory basis of off-host aggregation behavior.”


Saenz, V. L., R. G. Santangelo, E. L. Vargo, and C. Schal2014. Group living accelerates bed bug (Hemiptera: Cimicidae) development. Journal of Medical Entomology. 51: 293–295.

“For many insect species, group living provides physiological and behavioral benefits, including faster development. Bed bugs (Cimex lectularius L.) live in aggregations composed of eggs, nymphs, and adults of various ages. Our aim was to determine whether bed bug nymphs reared in groups develop faster than solitary nymphs. We reared first instars either in isolation or in groups from hatching to adult emergence and recorded their development time. In addition, we investigated the effects of group housing on same-age nymphs versus nymphs reared with adults. Nymphal development was 2.2 d faster in grouped nymphs than in solitary-housed nymphs, representing 7.3% faster overall development. However, this grouping effect did not appear to be influenced by group composition. Thus, similar to other gregarious insect species, nymph development in bed bugs is faster in aggregations than in isolation.”


Tatarnic, N. J., C. Gerasimos, and M. T. Silva-Jothy. 2014. Traumatic insemination in terrestrial arthropods. Annual Review of Entomology. 59:245-261. doi: 10.1146/annurev-ento-011613-162111

“Traumatic insemination is a bizarre form of mating practiced by some invertebrates in which males use hypodermic genitalia to penetrate their partner’s body wall during copulation, frequently bypassing the female genital tract and ejaculating into their blood system. The requirements for traumatic insemination to evolve are stringent, yet surprisingly it has arisen multiple times within invertebrates. In terrestrial arthropods traumatic insemination is most prevalent in the true bug infraorder Cimicomorpha, where it has evolved independently at least three times. Traumatic insemination is thought to occur in the Strepsiptera and has recently been recorded in fruit fly and spider lineages. We review the putative selective pressures that may have led to the evolution of traumatic insemination across these lineages, as well as the pressures that continue to drive divergence in male and female reproductive morphology and behavior. Traumatic insemination mechanisms and attributes are compared across independent lineages.”


2013

DeVries, Z. C., S. A. Kells, and A. G. Appel. 2013. Standard metabolic rate of the bed bug, Cimex lectularius: effects of temperature, mass, and life stage. Journal of Insect Physiology. 59(11): 1133–1139. doi: 10.1016/j.jinsphys.2013.08.012

“Metabolic rates provide important information about the biology of organisms. For ectothermic species such as insects, factors such as temperature and mass heavily influence metabolism, but these effects differ considerably between species. In this study we examined the standard metabolic rate of the bed bug, Cimex lectularius L. We used closed system respirometry and measured both O2 consumption and CO2 production across a range of temperatures (10, 20, 25, 30, 35°C) (50, 68, 77, 86, 95 °F) and life stages, while also accounting for activity. Temperature had a stronger effect on the mass specific .VO2 (mlg(-1)h(-1)) of mated males (Q10=3.29), mated females (Q10=3.19), unmated males (Q10=3.09), and nymphs that hatched (first instars, Q10=3.05) than on unmated females (Q10=2.77) and nymphs that molted (second through fifth instars, Q10=2.78). First instars had significantly lower respiratory quotients (RQ) than all other life stages. RQ of all stages was not affected by temperature. .VO2 (mlh(-1)) scaled more with mass than values previously reported for other arthropods or that would be predicted by the 3/4-power law. The results are used to understand the biology and ecology of the bed bug.”


Lange, R., K. Reinhardt, N. K. Michiels, and N. Anthes. 2013. Functions, diversity, and evolution of traumatic mating. Biological Reviews of the Cambridge Philosophical Society. 88: 585–601. doi: 10.1111/brv.12018

A literature review focusing on taxa that contain individuals that have evolved traumatic mating– copulation involving the wounding of the mating partner by specialised devices. Phyla discussed include Mollusca, Arthropoda, Nematoda, Chordota, and Rotifera. Traumatic mating likely evolved via several pathways.


Otti, O., A. P. McTighe, and K. Reinhardt. 2013. In vitro antimicrobial sperm protection by an ejaculate-like substance. Functional Ecology. 27: 219–226. doi: 10.111/1365-2435.12025

A bed bug ejaculate substance, lysozyme, decreased sperm death caused by sexually-transmitted environmental microbes, which is consistent with the antimicrobial sperm protection hypothesis. Lysozyme also stimulated early egg-laying above the female optimum and later caused earlier reproductive senescence in females. This is consistent with the idea that males transfer manipulative substances to females.


2012

Benoit, J. B., A. J. Jajack, and J. A. Yoder2012. Multiple traumatic insemination events reduce the ability of bed bug females to maintain water balance. Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. 182(2): 189–198. doi: 10.1007/s00360-011-0607-x

“To examine how traumatic insemination, a wounding process to females inflicted by males during copulation, reduces the longevity of females of the bedbug. Cimex lectularius, we assessed if multiple bouts of mating impact water relations of females by measuring net transpiration water loss rates. Our studies show that net transpiration rate of females correlates with frequency of mating (small increase after exposure to low numbers of males; large increase after exposure to large numbers of males), and this is reflected by reduced female survivorship for as much as 22 days at 75% RH, 25°C. Water loss occurs up to 28% more rapidly in females after being held with large groups of males. Females that were exposed to males having their paramere removed, females exposed only to other females, and females kept in isolation (unmated) exhibited no reduction in ability to retain water, indicating that traumatic insemination was responsible for the net transpiration rate increase. Mechanical piercing of the female’s abdominal wall leads to increased net transpiration rates for longer periods than puncturing the ectospermalege (regular mating site), implying that inaccurate copulation by males is extremely detrimental to the water balance of females and that the ectospermalege is uniquely modified to seal off more quickly to prevent excess water loss. Mating frequency and the associated increased water loss is considerably reduced by the addition of bed bug alarm pheromone components. Thus, females experience elevated water stress due to traumatic insemination, especially at high levels and when males fail to pierce the ectospermalege, and water loss prevention, likely by more rapid sealing of the wound, is a novel function of the ectopsermalege.”


Goddard, J., G. T. Baker, F. G. Ferrari, and C. Ferrari. 2012. Bed bugs (Cimex lectularius) and bat bugs (several Cimex species): a confusing issue. Outlooks on Pest Management. 23: 125–127. doi: 10.1564/23jun09

“Currently, bed bugs are one of the most pressing “vector” issues in pest control and environmental health, with increasing reports of the blood-sucking pest being reported in hotels, apartments, and single-family dwellings. Negative health effects from their bites include emotional distress (anxiety, insomnia, and perhaps even Posttraumatic stress disorder (PTSD)-like symptoms), nuisance bites and their associated cutaneous reactions, anemia, and potential disease transmission. Although bed bugs have been found naturally infected with a variety of disease agents, they have not been conclusively proven to transmit these organisms. Pest management professionals and environmental health specialists are on the front line of the bed bug battle, often being asked to investigate cases in private homes and apartments, as well as in public places such as hotels, hospitals, and schools. Compounding the issue is the fact that bat bugs may infest these places as well, especially if there are bats roosting in them (Usinger 1966). Bat bugs such as Cimex pipistrelli (Europe), Cimex pilosellus (western US), and Cimex adjunctus (entire eastern US) may sometimes bite people visiting or residing near the nesting or roosting sites of these species. Treatment/eradication strategies for bat bugs differ from that of bed bugs, and mainly involve solving the bat problem (not lethally, but by exclusion). Although bat bugs may occasionally bite humans, the bugs are not well-adapted to feeding on people. Bat bugs appear macroscopically identical to bed bugs, but closer examination can reveal differences. This article compares and contrasts identification of the bed bug, Cimex lectularius, and the commonly-encountered bat bug, Cimex adjunctus, and provides comments on treatment and control of each.”


Harraca, V., C. Ryne, G. Birgersson, and R. Ignell2012. Smelling your way to food: can bed bugs use our odour? Journal of Experimental Biology. 215: 623–629. doi: 10.1242/jeb.065748

“The resurgence in developed countries of the common bed bug, Cimex lectularius, has led to a search for new sustainable methods to monitor and control this human ectoparasite. Because of increased resistance to insecticides, traps baited with attractive cues are considered a promising method to be developed into efficient monitoring tools for bed bugs. Despite their potential as attractants, only a few studies have investigated the odorant cues implicated in the attraction of bed bugs to human hosts. In this study, we used aeration extracts from human volunteers to assess the role of olfaction in host searching by bed bugs. By coupled gas chromatography and single sensillum recordings on all the antennal sensilla, we measured the electrophysiological response elicited by the compounds present in our human odour extracts. Only five compounds were clearly detected by the olfactory receptor neurons housed in the smooth-peg sensilla of the bed bugs. We tested the behavioural effect of these extracts in a still-air arena and showed a gradient of repellence linked to the dose, as well as a higher propensity of local search behaviour associated with human odours containing a lower ratio of 6-methyl-5-hepten-2-one to C(7)-C(10) aldehydes. We conclude that human odour alone has a weak influence on the behaviour of C. lectularius and we propose that human kairomones may have a significant impact on bed bug behaviour in combination with heat and carbon dioxide, the only two currently known attractive vertebrate cues used by bed bugs for host seeking.”


Kilpinen, O., D. Liu, and A. P. S. Adamsen2012. Real-time measurement of volatile chemicals released by bed bugs during mating activities. PLoS One. 7(12): e50981. doi:10.1371/journal.pone.0050981

“In recent years, bed bug (Hemiptera: Cimicidae) problems have increased dramatically in many parts of the world, leading to a renewed interest in their chemical ecology. Most studies of bed bug semiochemicals have been based on the collection of volatiles over a period of time followed by chemical analysis. Here we present for the first time, a combination of proton transfer reaction mass spectrometry and video analysis for real-time measurement of semiochemicals emitted by isolated groups of bed bugs during specific behavioural activities. The most distinct peaks in the proton transfer reaction mass spectrometry recordings were always observed close to the termination of mating attempts, corresponding to the defensive emissions that bed bugs have been suspected to exploit for prevention of unwanted copulations. The main components of these emissions were (E)-2-hexenal and (E)-2-octenal recorded in ratios between 1:3 and 3:1. In the current study, the quantity varied over 1000 fold for both of the compounds with up to 40 µg total release in a single emission. Males also emit defensive compounds due to homosexual copulation attempts by other males, and no significant differences were observed in the ratio or the amount of the two components released from males or females. In summary, this study has demonstrated that combining proton-transfer-reaction mass spectrometry with video analysis can provide detailed information about semiochemicals emitted during specific behavioural activities.”


Seong, K. M., Y. H. Kim, D. H. Kwon, and S. H. Lee2012. Identification and characterization of three cholinesterases from the common bed bug, Cimex lectularius. Insect Molecular Biology. 21(2): 149–159. doi: 10.1111/j.1365-2583.2011.01118.x

“We identified and characterized the full-length cDNA sequences encoding two acetylcholinesterases (ClAChE1 and ClAChE2) and a salivary gland-specific cholinesterase-like protein (ClSChE) from the common bed bug, Cimex lectularius. All three cholinesterase genes (Clac1Clace2 and Clsce) have conserved motifs, including a catalytic triad, a choline-binding site and an acyl pocket. Phylogenetic analysis showed that ClAChE1 belongs to the insect AChE1 clade, whereas ClAChE2 belongs to the insect AChE2 clade. ClSChE was grouped into the clade containing all AChE1s, suggesting a paralogous relationship to ClAChE1. Transcription levels of Clace1 were higher than those of Clace2 in all tissues examined, including the central nervous system (CNS). In contrast, the Clsce transcript was not detected in the CNS but specifically found in the salivary gland at much higher levels (>3000-fold) than those of Clace1 and Clace2. Western blot analysis using anti-ClAChE antibodies, in conjunction with activity staining, revealed that ClAChE1 is more active than ClAChE2, whereas ClSChE has little enzyme activity. Three-dimensional structure modelling suggested that ClAChEs and ClSChE shared structural similarities, but had some differences in the residues forming the acyl pocket and oxyanion hole. The current findings should provide valuable insights into the evolution and functional diversification of insect cholinesterase.”


2011

Bai, X., P. Mamidala, S. P. Rajarapu, S. C. Jones, O. Mittapalli, and F. Marion-Poll. 2011. Transcriptomics of the bed bug (Cimex lectularius). PLoS ONE. 6(1): e16336. doi: 10.1371/journal.pone.0016336

Background: Bed bugs (Cimex lectularius) are blood-feeding insects poised to become one of the major pests in households throughout the United States. Resistance of C. lectularius to insecticides/pesticides is one factor thought to be involved in its sudden resurgence. Despite its high-impact status, scant knowledge exists at the genomic level for C. lectularius. Hence, we subjected the C. lectularius transcriptome to 454 pyrosequencing in order to identify potential genes involved in pesticide resistance. Methodology and Principal Findings: Using 454 pyrosequencing, we obtained a total of 216,419 reads with 79,596,412 bp, which were assembled into 35,646 expressed sequence tags (3902 contigs and 31744 singletons). Nearly 85.9% of the C. lectularius sequences showed similarity to insect sequences, but 44.8% of the deduced proteins of C. lectularius did not show similarity with sequences in the GenBank non-redundant database. KEGG analysis revealed putative members of several detoxification pathways involved in pesticide resistance. Lamprin domains, Protein Kinase domains, Protein Tyrosine Kinase domains and cytochrome P450 domains were among the top Pfam domains predicted for the C. lectularius sequences. An initial assessment of putative defense genes, including a cytochrome P450 and a glutathione-S-transferase (GST), revealed high transcript levels for the cytochrome P450 (CYP9) in pesticide-exposed versus pesticide-susceptible C. lectularius populations. A significant number of single nucleotide polymorphisms (296) and microsatellite loci (370) were predicted in the C. lectularius sequences. Furthermore, 59 putative sequences of Wolbachia were retrieved from the database. Conclusions: To our knowledge this is the first study to elucidate the genetic makeup of C. lectularius. This pyrosequencing effort provides clues to the identification of potential detoxification genes involved in pesticide resistance of C. lectularius and lays the foundation for future functional genomics studies.”


Benoit, J. 2011. Stress tolerance of bed bugs: A review of factors that cause trauma to Cimex lectularius and C. hemipterus. Insects. 2: 151–172. doi: 10.3390/insects2020151

A review of the literature concerning the different kinds of stresses that bed bugs encounter including dehydration, high humidity, temperature extremes, blood feeding, traumatic insemination (mating), microbial infections, and pesticide exposure. Their ability to resist stressful conditions has led to their expansion and proliferation.


Feldlaufer, M. F., and G. J. Blomquist. 2011. Cuticular hydrocarbons from the bed bug Cimex lectularius L. Biochemical Systematics and Ecology. 39: 283–285. doi: 10.1016/j.bse.2011.08.017

Mass spectrometry was used to determine the chemical composition of extracts from the surface (cuticle) of bed bugs. Seventeen hydrocarbons comprised 90% of the chemical composition of the extracts; adult males and females showed no differences in cuticular extracts.


Liedtke, H. C., K. Åbjörnsson, V. Harraca, J. T. Knudsen, E. A. Wallin, E. Hedenström, and C. Ryne2011. Alarm pheromones and chemical communication in nymphs of the tropical bed bug Cimex hemipterus (Hemiptera: Cimicidae). PLoS One. 6(3): e18156. doi: 10.1371/journal.pone.0018156

“The recent resurge of bed bug infestations (Cimex spp.; Cimicidae) and their resistance to commonly used pesticides calls for alternative methods of control. Pheromones play an important role in environmentally sustainable methods for the management of many pest insects and may therefore be applicable for the control of bed bugs. The tropical bed bug, Cimex hemipterus, is a temporary ectoparasite on humans and causes severe discomfort. Compared to the common bed bug, Cimex lectularius, little is known about the chemical signaling and pheromone-based behaviour of the tropical species. Here, we show that the antennal morphology and volatile emission of C. hemipterus closely resembles those of C. lectularius and we test their behavioural responses to conspecific odour emissions. Two major volatiles are emitted by male, female and nymph C. hemipterus under stress, (E)-2-hexenal and (E)-2-octenal. Notably, nymph emissions show contrasting ratios of these compounds to adults and are further characterized by the addition of 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal. The discovery of this nymph pheromone in C. hemipterus is potentially the cause of a repellent effect observed in the bio-tests, where nymph odours induce a significantly stronger repellent reaction in conspecifics than adult odours. Our results suggest that pheromone-based pest control methods developed for C. lectularius could be applicable to C. hemipterus, with the unique nymph blend showing promising practical properties.”


Mamidala, P., S. P. Rajarapu, S. C. Jones, and O. Mittapalli2011. Identification and validation of reference genes for quantitative real-time polymerase chain reaction in Cimex lectularius. Journal of Medical Entomology. 48: 947–951. doi: 10.1603/ME10262

“Quantitative real-time polymerase chain reaction (qRT-PCR) has emerged as robust methodology for gene expression studies, but reference genes are crucial for accurate normalization. Commonly used reference genes are housekeeping genes that are thought to be nonregulated; however, their expression can be unstable across different experimental conditions. We report the identification and validation of suitable reference genes in the bed bug, Cimex lectularius, by using qRT-PCR. The expression stability of eight reference genes in different tissues (abdominal cuticle, midgut, Malpighian tubules, and ovary) and developmental stages (early instar nymphs, late instar nymphs, and adults) of pesticide-susceptible and pesticide-exposed C. lectularius were analyzed using geNorm, NormFinder, and BestKeeper. Overall expression analysis of the eight reference genes revealed significant variation among samples, indicating the necessity of validating suitable reference genes for accurate quantification of mRNA transcripts. Ribosomal protein (RPL18) exhibited the most stable gene expression across all the tissue and developmental-stage samples; α-tubulin revealed the least stability across all of the samples examined. Thus, we recommend RPL18 as a suitable reference gene for normalization in gene expression studies of C. lectularius.”


Reinhardt, K., R. Naylor, and M. T. Siva-Jothy2011. Male mating rate is constrained by seminal fluid availability in bedbugs, Cimex lectularius. PLoS One. 6: e22082. doi: 10.1371/journal.pone.0022082

“Sexual selection, differences in reproductive success between individuals, continues beyond acquiring a mating partner and affects ejaculate size and composition (sperm competition). Sperm and seminal fluid have very different roles in sperm competition but both components encompass production costs for the male. Theoretical models predict that males should spend ejaculate components prudently and differently for sperm and seminal fluid but empirical evidence for independent variation of sperm number and seminal fluid volume is scarce. It is also largely unknown how sperm and seminal fluid variation affect future mating rate. In bedbugs we developed a protocol to examine the role of seminal fluids in ejaculate allocation and its effect on future male mating rate. Using age-related changes in sperm and seminal fluid volume we estimated the lowest capacity at which mating activity started. We then showed that sexually active males allocate 12% of their sperm and 19% of their seminal fluid volume per mating and predicted that males would be depleted of seminal fluid but not of sperm. We tested (and confirmed) this prediction empirically. Finally, the slightly faster replenishment of seminal fluid compared to sperm did not outweigh the faster decrease during mating. Our results suggest that male mating rate can be constrained by the availability of seminal fluids. Our protocol might be applicable to a range of other organisms. We discuss the idea that economic considerations in sexual conflict research might benefit from distinguishing between costs and benefits that are ejaculate dose-dependent and those that are frequency-dependent on the mating rate per se.”


Szalanski, A. L., A. D. Tripodi, and J. W. Austin2011. Multiplex polymerase chain reaction diagnostics of bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. 48: 937–940. doi: 10.1603/ME10251

Cimex lectularius L. (Hemiptera: Cimicidae) is a widespread blood feeding pest of humans around the world, including North America, and has recently undergone a resurgence. A molecular diagnostic technique applying multiplex polymerase chain reaction (PCR) was developed to distinguish bed bug eggs, leg fragments, and degraded samples from other arthropods that frequently occur in human dwellings. A 410–428-bp region of the mitochondrial DNA 16S rRNA gene was used. To design C. lectularius-specific PCR primers, DNA sequences of various bed bug samples from the United States, Canada, and Australia, along with sequences of other Cimicidae and arthropods that often occur in dwellings, were considered. Based on DNA sequence variation, one reverse PCR primer specific for C. lectularius was identified. Multiplex PCR using three primers will yield a 417- and 140-bp amplicon for C. lectularius and a single 410–428-bp amplicon for other taxa. This assay was successful in identifying C. lectularius eggs, leg fragments, and degraded samples. This technique should provide a reliable, quick, and economical technique for identifying C. lectularius, when morphological identification is not possible.”


Weeks, E. N. I., J. G. Logan, S. A. Gezan, C. M. Woodcock, M. A. Birkett, J. A. Pickett, and M. M. Cameron. 2011. A bioassay for studying behavioural responses of the common bed bug, Cimex lectularius (Hemiptera: Cimicidae) to bed bug-derived volatiles. Bulletin of Entomological Research. 101: 1–8. doi: 10.1017/S0007485309990599

“The common bed bug, Cimex lectularius (Hemiptera: Cimicidae), has recently re-emerged in increasing numbers, distribution and intensity of infestation in many countries. Current control relies on the application of residual pesticides; but, due to the development of insecticide resistance, there is a need for new tools and techniques. Semiochemicals (behaviour and physiology modifying chemicals) could be exploited for management of bed bugs. However, in order to identify semiochemicals that can be utilised in monitoring or control, a suitable olfactometer is needed that enables the study of the responses of bed bugs to volatile chemicals. Previous studies have used olfactometers that do not separate olfactory responses from responses to physical contact. In this study, a still-air olfactometer was used to measure behavioural responses to different bed bug-derived volatiles presented in an odour pot. Bed bugs were significantly more likely to visit the area above the odour pot first, and more frequently, in the presence of volatiles from bed bug-exposed paper but not in the presence of volatiles from conspecific bed bugs. Bed bug activity was found to be dependent on the presence of the volatiles from bed bug-exposed paper, the time during the scotophase and the sex of the insect being tested. The still-air olfactometer could be used to test putative semiochemicals, which would allow an understanding of their behavioural role in bed bug ecology. Ultimately, this could lead to the identification of new semiochemical tools for bed bug monitoring and control.”


2010

Domingue, M. J., M. Kramer, and M. F. Feldlaufer. 2010. Sexual dimorphism of arrestment and gregariousness in the bed bug (Cimex lectularius) in response to cuticular extracts from nymphal exuviae. Physiological Entomology. 35: 203–213. doi: 10.1111/j.1365-3032.3010.00738.x

Researchers described bed bug gregariousness and arrestment behavior (settling near the odor source) in response to chemical extracts from the shed skins (exuviae) of other bed bugs (conspecifics). Adult males and females exhibited different behaviors. Adult males settled near the extracts from fifth stage nymphs, whereas adult females grouped together without any tendency to assemble near the odor source.


Feldlaufer, M. F., M. J. Domingue, K. R. Chauhan, and J. R. Aldrich. 2010. 4-oxo-aldehydes from the dorsal abdominal glands of the bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. 47: 140–143. doi: 10.1093/jmedent/47.2.140

“Analyses of the dorsal abdominal glands of fourth- and fifth-instar nymphs of the bed bud, Cimex lectularius L. (Hemiptera: Cimicidae), indicated the predominant constituents were (E)-2-hexenal and (E)-2-octenal, with lesser amounts of 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal. The latter two compounds have not been reported previously as occurring in bed bugs. There were no differences in the chemical composition of the dorsal abdominal glands excised from exuviae left behind by either male or female adults, nor from glands excised from fourth-instar exuviae. Because the two oxo-aldehydes made up at least 16% of the gland contents, further study of the functional role of these chemicals seem advisable.”


Francischetti, I. M. B., E. Calvo, J. F. Andersen, V. M. Pham, A. J. Favreau, K. D. Barbian, A. Romero, J. G. Valenzuela, and J. M. C. Ribeiro. 2010. An insight into the sialome of the bed bug, Cimex lectularius. Journal of Proteome Research. 9: 3820–3831. doi: 10.1021/pr1000169

“The evolution of insects to a blood diet leads to the development of a saliva that antagonizes their hosts’ hemostasis and inflammation. Hemostasis and inflammation are redundant processes, and thus a complex salivary potion comprised of dozens or near one hundred different polypeptides is commonly found by transcriptome or proteome analysis of these organisms. Several insect orders or families evolved independently to hematophagy creating unique salivary potions in the form of novel pharmacological use of endogenous substances, and in the form of unique proteins not matching other known proteins, these probably arriving by fast evolution of salivary proteins as they evade their hosts’ immune response. In this work we present a preliminary description of the sialome (from the Greek Sialo = saliva) of the common bed bug Cimex lectularius, the first such work from a member of the Cimicidae family.”


Harraca, V., C. Ryne, and R. Ignell2010. Nymphs of the common bed bug (Cimex lectularius) produce anti-aphrodisiac defence against conspecific males. BioMed Central Biology. 8: 1–7. doi: 10.1186/1741-7007-8-121

“BACKGROUND: Abdominal wounding by traumatic insemination and the lack of a long distance attraction pheromone set the scene for unusual sexual signaling systems. Male bed bugs (Cimex lectularius) mount any large, newly fed individual in an attempt to mate. Last instar nymphs overlap in size with mature females, which make them a potential target for interested males. However, nymphs lack the female’s specific mating adaptations and may be severely injured by the abdominal wounding. We, therefore, hypothesized that nymphs emit chemical deterrents that act as an honest status signal, which prevents nymph sexual harassment and indirectly reduces energy costs for males. RESULTS: Behavioural mating assays showed that males mount nymphs significantly shorter time compared to females, although initial mounting preference was the same. In support of our hypothesis, nymphs experienced the same percentage of mating with sperm transfer as females if they were unable to emit (E)-2-hexenal, (E)-2-octenal 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal, from their dorsal abdominal glands. We report that the aldehydes and 4-oxo-(E)-2-hexenal are detected by olfactory receptor neurons housed in smooth and grooved peg sensilla, respectively, on the adult antennae, at biologically relevant concentrations. Behavioural experiments showed that application of 4-oxo-(E)-2-hexenal or the two aldehydes at a nymph-emitted ratio, to a male/female pair during mounting initiation, decreased mating frequency to a rate comparable to that of a male/nymph pair. CONCLUSIONS: By combining behavioural and sensory studies, we show that the nymph-specific alarm pheromone plays an important role in intra-specific communication in the common bed bug. Alarm pheromones are commonly looked upon as a system in predator/prey communication, but here we show that alarm pheromones may be used as multipurpose signals such as decreasing the risk of nymphal mating by males.” 


Haynes, K. F., M. H. Goodman, and M. F. Potter2010. Bed bug deterrence. BioMed Central Biology. 8:117. doi: 10.1186/1741-7007-8-117.

This commentary highlights the 2010 article by Harraca and colleagues in BMC Biology (doi: 10.1186/1741-7007-8-121) wherein they reported that bed bug immatures (nymphs) used pheromones to signal their reproductive status to adult males, thereby avoiding the trauma associated with copulation (traumatic insemination) in this species. The implications of chemical signaling in bed bugs and the role of pheromones in potential control strategies are discussed.


Hosokawa, T., R. Koga, Y. Kikuchi, X.-Y. Meng, and T. Fukatsu. 2010. Wolbachia as a bacteriocyte-associated nutritional mutualist. Proceedings of the National Academy of Sciences. 107: 769–774. doi: 10.1073/pnas.0911476107

Molecular techniques were used to explore the relationship between Wolbachia, a bacterial symbiont, and bed bugs. In many insects, including bed bugs, symbionts are harbored in specific cells called bacteriocytes that constitute a symbiotic organ bacteriome. Two bacterial symbionts, a Wolbachia strain and an unnamed gamma-proteobacterium, were identified from different bed bug strains. The Wolbachia symbiont was vertically transmitted to eggs and its loss resulted in bed bug retarded growth and sterility. These deficiencies were rescued by oral uptake B vitamins, confirming that Wolbachia was an obligate nutritional mutualist.


How, Y.-F., and C.-Y. Lee2010. Effects of temperature and humidity on the survival and water loss of Cimex hemipterus (Hemiptera: Cimicidae). Journal of Medical Entomology. 47: 987–995. doi: 10.1603/ME10018 987-995

“Two field-collected strains of the tropical bed bug, Cimex hemipterus (F.), were exposed to temperatures ranging from 20º to 45ºC (68º to 113ºF) and 33, 75, and 100% relative humidity (RH). Tropical bed bugs survived longest under the interaction of low temperature (20ºC) (68ºF) and high RH (75-100%). Survival and water loss were significantly affected by temperature and RH (either singly or in interaction). Bed bug strain and sex significantly influenced bed bug survival, but not water loss. Eggs, first stage nymphs, and adults reached their upper thermal lethal limit within 1 hr at 39ºC (102ºF), 44ºC (111ºF), and 46ºC (114.8ºF), respectively. Survival and water loss profiles indicated that starved bugs started to die after losing 35-45% body weight.


Reinhardt, K., D. Isaac, and R. Naylor2010. Estimating the feeding rate of the bedbug Cimex lectularius in an infested room: an inexpensive method and a case study. Medical and Veterinary Entomology. 24: 46–54. doi: 10.1111/j.1365-2915.2009.00847.x

Researchers present a method of estimating the average time since the last blood meal of individual female bed bugs in a single sampling event, applicable to a single bed bug harborage or an entire room. The method is cheap and rapid and should be widely applicable as it corrects for variations in body size across different bed bug populations and determines shrinkage that occurs when bugs are preserved in ethanol. When coupled with information on the total number of bed bugs present in a room, the method allows for estimating the minimum number of times persons lodging in a room have been bitten by bed bugs. In the described case study, using the temperature-dependent rate of decrease in the abdomen size of the bed bug after a blood meal, it was determined that females fed every 2.5 d on average in a highly infested room maintained at 26 ºC (78.8ºF). The sex ratio in the infestation was female-biased. This case study suggests that individual female bed bugs within a harborage apparently do not feed at a regular rate, but tend to synchronize feeding patterns.


Romero, A., M. F. Potter, and K. F. Haynes. 2010. Circadian rhythm of spontaneous locomotor activity in the bed bug, Cimex lectularius L. Journal of Insect Physiology. 56: 1516–1522. doi: 10.1016/j.jinsphys.2010.04.025

“Bed bugs must avoid detection when finding hosts and returning to hidden harborages. Their stealthy habits include foraging when hosts are asleep. Characteristics of spontaneous locomotor activity rhythm of bed bugs with different feeding histories were studied. In the absence of host stimuli, adults and nymphs were much more active in the dark than in the light. The onset of activity in the scotophase commenced soon after lights-off. The free-running period (τ) for all stages was longer in continuous darkness (DD) than in continuous light (LL). The lengthening of τ in DD is an exception for the circadian rule that predicts the opposite in nocturnal animals. Activity in all stages was entrained to reverse L:D regimes within four cycles. Short-term starved adults moved more frequently than recently fed adults. While bed bugs can survive for a year or more without a blood meal, we observed a reduction in activity in insects held for five weeks without food. We suggest that bed bugs make a transition to host-stimulus dependent searching when host presence is not predictable. Such a strategy would enable bed bugs to maximize reproduction when resources are abundant and save energy when resources are scarce.”


2009

Reinhardt, K., C. H. Wong, and A. S. Georgiou. 2009. Detection of seminal fluid proteins in the bed bug, Cimex lectularius, using two-dimensional gel electrophoresis and mass spectrometry. Parasitology. 136: 283-292. doi: 10.1017/S0031182008005362

“The global increase of the human parasite, the common bed bug Cimex lectularius, calls for specific pest control target sites. The bed bug is also a model species for sexual conflict theory which suggests that seminal fluids may be highly diverse. The species has a highly unusual sperm biology and seminal proteins may have unique functions. One-dimensional PAGE gels showed 40–50% band sharing between C. lectularius and another cimicid species, Afrocimex constrictus. However, adult, sexually rested C. lectularius males were found to store 5–7 μg of seminal protein and with only 60 μg of protein we obtained informative 2-D PAGE gels. These showed 79% shared protein spots between 2 laboratory populations, and more than half of the shared protein spots were detected in the mated female. Further analysis using liquid chromatography electrospray ionization tandem mass spectrometry revealed that 26·5% of the proteins had matches among arthropods in databases and 14·5% matched Drosophila proteins. These included ubiquitous proteins but also those more closely associated with reproduction such as moj 29, ubiquitin, the stress-related elongation factor EF-1alpha, a protein disulfide isomerase and an antioxidant, Peroxiredoxin 6.”


Ryne, C. 2009. Homosexual interactions in bed bugs: alarm pheromones as male recognition signals. Animal Behavior. 78(6): 1471–1475. doi: 10.1016/j.anbehav.2009.09.033

“Homosexual mounting is a common behaviour in bed bugs as male sexual interest is directed towards any newly fed individual. The only mode of copulation in the common bed bug, Cimex lectularius,is by traumatic insemination, where the male pierces the female abdomen with his needle-like penis. Homosexual mating would result in abdominal injuries in mounted males, as males lack the female counter adaptive spermalege structure. I here show that bed bug alarm pheromones, previously hypothesized to be a predator chemical defence, can be used by newly fed males to signal their sex and reduce the risk of homosexual mating. Mechanical blocking of the male pheromone glands significantly increased homosexual mounting duration compared to control males, while applying male extracts containing mainly alarm pheromone onto male–female mating pairs completely interrupted or shortened mating duration and reduced sperm transfer. Males confined with other males received piercing scars, demonstrating that homosexual mating occurs. The focal males in the all-male confinement experiment had reduced longevity compared to singly held males, but why this reduction in longevity occurred is not clear. Mounted males thus benefit from being able to discharge alarm pheromones, while mounting males consider the alarm signal a major sex identification cue, suggesting that male bed bugs use alarm pheromone communication to avoid homosexual harassment and mounting.”


2008


2007

Reinhardt, K., and M. T. Siva-Jothy. 2007. Biology of the bed bugs (Cimicidae). Annual Review of Entomology. 52: 351–374. doi: 10.1146/annurev.ento.52.040306.133913

A literature review focusing on issues relevant to pest control, such as bed bug biology, dispersal ecology, and the recent global spread.


2006

Siva-Jothy, M. T. 2006. Trauma, disease and collateral damage: conflict in cimicids. Philos. Trans. R. Soc. B-Biol. Sci. 361(1466): 269-275. doi: 10.1098/rstb.2005.1789

“The ability to identify individual human hosts based on analyses of blood recovered from hematophagous insects is beneficial for both medical and forensic entomology. Bed bugs, Cimex lectularius L. (Heteroptera: Cimicidae), may have several advantages over other blood-feeding arthropods for forensics because they do not remain on the host after their blood-feeding activity and remain in close proximity to a crime scene. Successful isolation, amplification and sequencing of human DNA obtained from adult bed bugs is reported for the first time from this study. Engorged bed bugs were recovered from a human volunteer and from field collected samples from New York, New York, and Brazos County, Texas. Samples were preserved by drying, stored in 70% ethanol, or freezing at -20 C (-4 ºF). DNA was extracted from individual insects, and polymerase chain reaction was conducted using short tandem repeat (STR), human mitochondrial DNA (mtDNA) hypervariable region (HVR1), and insect mdDNA 16S markers. Amplification of a STR marker used in forensic investigations, D18S51, a HVR1 marker, and an insect mdDNA 16S marker was successful. These results demonstrate that DNA isolated from bed bugs is qualitatively and quantitatively sufficient for DNA typing and could be helpful to identify individuals for forensic analysis.”


Szalanski, A. L., J. W. Austin, J. A. McKern, C. D. Steelman, Dayton, D. M. Miller, and R. E. Gold2006. Isolation and characterization of human DNA from bed bug, Cimex lectularius L., (Hemiptera: Cimicidae) blood meals. Journal of Agricultural and Urban Entomology. 23: 189–194.

“The ability to identify individual human hosts based on analyses of blood recovered from hematophagous insects is beneficial for both medical and forensic entomology. Bed bugs, Cimex lectularius L. (Heteroptera: Cimicidae), may have several advantages over other blood-feeding arthropods for forensics because they do not remain on the host after their blood-feeding activity and remain in close proximity to a crime scene. Successful isolation, amplification and sequencing of human DNA obtained from adult bed bugs is reported for the first time from this study. Engorged bed bugs were recovered from a human volunteer and from field collected samples from New York, New York, and Brazos County, Texas. Samples were preserved by drying, stored in 70% ethanol, or freezing at -20 C (-4 ºF). DNA was extracted from individual insects, and polymerase chain reaction was conducted using short tandem repeat (STR), human mitochondrial DNA (mtDNA) hypervariable region (HVR1), and insect mdDNA 16S markers. Amplification of a STR marker used in forensic investigations, D18S51, a HVR1 marker, and an insect mdDNA 16S marker was successful. These results demonstrate that DNA isolated from bed bugs is qualitatively and quantitatively sufficient for DNA typing and could be helpful to identify individuals for forensic analysis.”


2005


2003

Morrow, E. H., and G. Arnqvist2003. Costly traumatic insemination and a female counter-adaptation in bed bugs. Proceedings of the Royal Society B-Biological Sciences. 270(1531): 2377-2381. doi: 10.1098/rspb.2003.2514

“Male bed bugs pierce females through the body wall and inseminate directly into the body cavity. It has previously been shown that such traumatic insemination carries costs for females, and sexual conflict regarding the mode of insemination should thus propel male-female coevolution. Since males accumulate sexually antagonistic adaptations, females should evolve counter-adaptations that efficiently abate the costs to females of sexual interactions. Yet, unambiguous experimental evidence for female counter-adaptations is lacking. In bed bugs, the spermalege (a highly modified region of the abdomen where the male usually pierces the female) may represent a female counter-adaptation. We assess the female costs of traumatic insemination by varying the rate of insemination on the one hand, and the rate and mode of piercing trauma to females on the other. Our results show that female mating costs are not extreme-elevated mating rate shortened female lifespan but had no significant effect on lifetime egg production. More importantly, additional abdominal piercing in the spermalege had no effect on females whereas even a very low rate of such piercing outside the spermalege reduced female lifetime egg production by 50%. Thus, females are well counter-adapted to the intrusive mode of insemination exhibited by male bed bugs and the costs of elevated mating are comparable with those in other insects, as predicted by theory. We therefore demonstrate that the spermalege efficiently reduces the direct costs of piercing trauma to females, and hence provide experimental evidence for a female counter-adaptation to a sexually antagonistic male trait.”


1941

Johnson, C. G. 1941. The ecology of the bed-bug, Cimex lectularius L., in Britain. Journal of Hygiene. 41: 345–461. doi: 10.1017/S0022172400012560

“In 1934 a committee on the eradication of bed-bugs appointed by the Minister of Health issued its report (Report on the Bed-bug, 1934) in which recommendations for research into the biology of Cimex lectularius L. were made. The committee was struck by the lack of precise information on certain aspects of the bionomics and habits of the insect and suggested work along the following lines: 1) The effect of food supply and starvation at different seasons and at different stages of development. 2) The periods of survival of bed-bugs and their eggs under different conditions. 3) The extent to which bed-bugs can subsist on the blood of birds, bats, mice, etc., when deprived of human blood. 4) The position and types of harbourages most favoured by bed-bugs under different conditions. 5) The distance which bed-bugs will travel, the factors (warmth, smell, etc.) which attract them, and whether they habitually return to the same harbourage.”


1939

Mellanby, K. 1939. The physiology and activity of the bed-bug (Cimex lectularius L.) in a natural infestation. Parasitology. 31: 200–211. doi: 10.1017/S0031182000012762

Researchers studied a natural bed bug population that had existed by feeding on caged rats in an animal room for several years. The bugs were trapped during their periods of normal activity. The bugs were most active between 3-6 am. Adult bed bugs fed on the rats about once every 5 or-6 days at temperatures of 20-27ºC (68-80 ºF). Females laid eggs in series of three/day. The females in this wild population mated about once a week whereas copulation occurs much more frequently in laboratory cultures. The population was roughly estimated from mark-release experiments. The majority of adults did not live more than 29 days, presumably due to rats killing the bugs that were trying to get a blood meal.