Explaining Science – vermiform mites

You have heard of mites – minute arachnids that have four pairs of legs when adult, are related to the ticks and live in the soil, though some are parasitic on plants or animals. But what are vermiform mites? Maybe you have heard of vermi-compost, a composting technique that uses worms (like your earthworm in the garden) to decompose organic matter. So vermiform mites are mites with a body shape like a worm:

worm-shaped nematalycid Osperalycus

Why are they shaped like a worm, you may ask – To find out more I interviewed Samuel Bolton, former PhD student in the acarology collection at our museum, now Curator of Mites at the Florida State Collection of Arthropods. Sam’s main research interest is in mites that live on plants and in the soil, especially Endeostigmata, a very ancient group of mites that dates back around 400 million years, before there were any trees or forests. Sam’s PhD research with Dr. Hans Klompen here at OSU, was focused on a small family (only five described species) of worm-like mites, called Nematalycidae.

side note: You may have heard of Sam’s research in 2014 when he discovered a new species of mite, not in a far-away country, but across the road from his work place in the museum.

When Sam started his research it was not clear where these worm-like mites in the family Nematalycidae belong in the tree of life. To find out Sam studied several morphological characters of Nematalycidae and other mites. He focused in particular on the mouth-parts of this group. As he learned more about the mouth-parts of this family, he found evidence that they are closely related to another lineage of worm-like mites, the gall mites (Eriophyoidea). Eriophyoidea have a sheath that wraps up a large bundle of stylets. They use these stylets to pierce plant cells, inject saliva into them and suck cell sap.
Although Nematalycidae don’t have stylets, one genus has a very rudimentary type of sheath that extends around part of the pincer-like structures that have been modified into stylets in Eriophyoidea.

So what did Sam and his co-authors discover?

“.. Not only are gall mites the closest related group to Nematalycidae, but the results of our phylogenetic analysis places them within Nematalycidae. This suggests that gall mites are an unusual group of nematalycids that have adapted to feeding and living on plants. Gall mites use their worm-like body in a completely different way from Nematalycidae, which live in deep soil. But both lineages appear to use their worm-like bodies to move around in confined spaces: gall mites can live in the confined spaces in galls, under the epidermis (skin), and in between densely packed trichomes on the surface of leaves;  Nematalycidae live in the tight spaces between the densely packed mineral particles deep in the soil.”

This research potentially increases the size of Sam’s family of expertise, Nematalycidae, from 5 species to 5,000 species. We have yet to confirm this discovery, but it is highly likely that gall mites are closely related to Nematalycidae, even if they are not descended from Nematalycidae. This is interesting because it shows that the worm-like body form evolved less frequently than we thought. This discovery also provides an interesting clue about how gall mites may have originated to become parasites. They may have started out in deep soil as highly elongated mites. When they began feeding on plants, they may have used their worm-shaped bodies to live underneath the epidermis of plants. As they diversified, many of them became shorter and more compact in body shape.

I wish I could tell you now to go out and look for these oddly shaped mites yourself, but you really need a microscope. Eriophyoid mites are minute, averaging 100 to 500 μm in length. For your reference, an average human hair has a diameter of 100 microns.

eriophyoid Aceria anthocoptes


Bolton, S. J., Chetverikov, P. E., & Klompen, H. (2017). Morphological support for a clade comprising two vermiform mite lineages: Eriophyoidea (Acariformes) and Nematalycidae (Acariformes). Systematic and Applied Acarology, 22(8), 1096-1131.


About the Authors: Angelika Nelson, curator of the Borror Laboratory of Bioacoustics, interviewed Samuel Bolton, former PhD graduate student in the OSU Acarology lab, now Curator of Mites at the Florida State Collection of Arthropods, in the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry.


Itchy noses – a perfect ecosystem for mites & ticks?

Mites on occasion have become extreme specialists in selecting the places where they live. Take the noses of vertebrates. It may not seem much, but a wide variety of mites call it home. Mites can do different things while in the nose. Rhinoseius and some Proctolaelaps species use hummingbird noses to move from flower to flower.

hummingbird sticking bill into red flower

Hummingbird sticking its “nose” into a flower (did you know that the nostrils of birds are located at the base of the bill?)

The mites race up or down the bill when the bird is feeding to get in or out of the nose as they move between flowers. Nice and fast transportation but it can be tricky. If a male ends up in a flower already occupied by males of a different species they may get attacked and killed. As always make sure you get off at the right bus stop.

Dispersal is also the goal for some Halarachnidae living in seals. They live most of their lives in the lungs, but larvae will crawl up into the nose and get dispersed by sneezing. It is not sure whether they irritate the nose and make the seals sneeze or whether they just take advantage of seal sneezing.  This form of dispersal is of course a bit random.  For example, a paper from 1985 described a case where an ophthalmologist recovered a halarachnid mite from the eye of a patient with severe eye discomfort.  The man had been watching the walrus exhibit at Sea World.  Moral of the story: be aware of flying debris when visiting the seal exhibit.

Most nose-inhabiting mites are true parasites. Some chiggers (Trombiculidae) are found only in noses. So do most species of Gastronyssidae, although I have collected some skating around on the eyeball of fruitbats, and 1-2 others appear exclusive to the stomach of such bats. In birds we sometimes see a split in microhabitat: Rhinonyssidae live in the slimy parts of the nostrils, Ereynetidae skate on top of the slime, and Turbinoptidae live in the dryer section further down.

rhinonyssid mite from nose of pigeon

Rhinonyssid mite from nose of pigeon

Noses are true ecosystems.


About the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of the Ohio State University Acarology Collection.



Webb, J.P., Jr., Furman, D.P. & Wang, S. (1985) A unique case of human ophthalmic acariasis caused by Orthohalarachne attenuata (Banks, 1910) (Acari: Halarachnidae). Journal of Parasitology, 71 (3), 388-389.

Mite art

The Berlese Alphabet

These letters are from the four-volume “Acaroteca” of Antonio Berlese, (1863-1927) in which he maintained records of his named specimens. Berlese illustrated this catalogue with a large letter at the beginning of each section. The mites are examples of those whose genus name begins with that letter. Not all letters were completed before his death, and several pages have been heavily stained.

Norton, 2008

The Berlese Alphabet

Following up on unusual ways to treat (or image) mites, here is an example that is both beautiful and very traditional, following the medieval tradition of illuminated letters. This image is of a poster assembled by Roy Norton featuring most of the letters of the Berlese alphabet. In case you have never heard of Berlese, Antonio Berlese was an Italian entomologist (1863 – 1927) who studied agricultural pest insects. He put together a catalogue of his collection of mites, referred to as the Catalogue of the Berlese Acaroteca. He included about 1600 species, the entries are arranged alphabetically by species according to Berlese’s final specific and generic concept. Each section begins with a large letter featuring a mite whose genus name begins with that letter.

letter M with images of mites from the Berlese alphabet

Letter M from the Berlese Alphabet, © Cal Welbourn

The individual drawings are simply gorgeous, and most specimens can easily be identified to genus. Of course many generic names have changed since early 20th century, so I would not recommend this as a work of taxonomy, but the Berlese alphabet remains a great work of “mite art”.


About the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of the Ohio State University Acarology Collection.

Mites and moths

Following some earlier blogs about recently acquired collections I present to you here the Treat collection. This collection was assembled by Asher E. Treat a researcher at City University of New York and the American Museum of Natural History, also New York. This collection is one of the best in the world for mites associated with Lepidoptera (butterflies and moths). Mites have been found associated with most terrestrial and many aquatic organisms, but when it comes to insect hosts, mites on Coleoptera (beetles) and Hymenoptera (bees and wasps) are clearly the most numerous, diverse, and well-known. Still, Lepidoptera have a variety of associated mites.

The Acarology Collection acquired this collection 4 years ago, some years after Treat’s death. The collection consisted of about 37 slide boxes of exceptionally well labelled microscope slides and half a dozen insect drawers of pinned moths (all labelled as hosts of specific mite specimens). The Lepidoptera are being processed at the Triplehorn Insect collection, while we, the Acarology collection, have been working on processing (mostly databasing) the slides. This is proving to be a major job.


Image of a female of Dicrocheles phalaenodectes, the moth ear mite

Image of a female of Dicrocheles phalaenodectes, the moth ear mite

Treat got interested in mites associated with moths after finding mites in the ears of noctuid moths. In the process, he figured out the quite amazing life histories of some mites associated with these moths. The most famous is Dicrocheles phalaenodectes, the moth ear mite (family Laelapidae).

These mites break through the tympanic membrane of the ear of the moth and form small colonies inside the ear. By itself not too surprising, but the interesting part Treat discovered was that these mites are always found in one ear only, rarely if ever in both ears. In a way this makes sense. By breaking the tympanic membrane the mites make the moth deaf in that ear. Moths need their hearing to avoid predators (for example bats) so a deaf moth would be easy prey. However, a moth with one functional ear is still able to avoid bats, perhaps not as well as if it had two functional ears, but close enough. Which leaves the question: how do the mites manage to limit infestations to one ear?

Treat did many careful observations and follow-up experiments on this aspect and found that the mites have a very specific set of behaviors ensuring only one ear will be parasitized. The first female to get on a moth (nearly always a fertilized female, the immatures and males do not colonize) crawls to the dorsal part of the thorax, explores a little, after which she proceeds to one ear. Any future colonizers will first go to that same dorsal part of the thorax of the moth and follow the initial female to the same ear. It appears the mites lay a pheromone trail that guides newcomers to the already infested ear, and away from the uninfested one.

Drawing of relative positions of mites in a moth ear

Drawing of relative positions of mites in a moth ear

To complete the cycle, young females leaving the ear initially wander around the hosts body (mostly the thorax), congregating around the head at night. They leave the moth by running down its proboscis when it is feeding on flowers. On the flowers, the mites wait for their next host.
Another mite family that is specialized on Lepidoptera, the Otopheidomenidae, is also parasitic, and they will also show up near the ears, but they do not pierce the tympanic membrane, so they do not cause deafness. Unfortunately, we know much less about them, Treat was never able to study their behavior. A range of other mite families have representatives that are regularly found on Lepidoptera, but they are not specialists at the family level: Ameroseiidae, Melicharidae, Erythraeidae, Iolinidae, Cheyletidae, Acaridae, Carpoglyphidae, and Histiostomatidae. That list excludes the occasional “vagrants” that can be found on moths, but that are unlikely to be living on them for extended periods of time. All in all, quite a diverse community.
For those interested in knowing more, Treat wrote a book “Mites of Moths and Butterflies” (1975, Cornell University Press) that is a rare combination of good scholarship (especially natural history) and readability.

Title page of Treat's book on moth mites

Title page of Treat’s book on moth mites

Treat was very careful and noted things like host specimen numbers (if available), which allows current researchers to track down the exact moth from which a given mite came.

This is currently a common approach, but Treat started this in the 1950-ies. And there is more. Based on Treat’s label data we know not only the name of the hosts and the specific locality, but also gender of the host, whether the left or right ear was infested, and the exact part of the body the mites were found on. So we have excellent information, directly from the slides, showing that Proctolaelaps species (family Melicharidae) are nearly always found near the base of the palps [as an aside, Proctolaelaps is a bit of an unfortunate generic name, combining “procto-” = anus and “laelaps” = hurricane; presumably the name

Microscope slide from the Treat collection

Slide from the Treat collection

refers to a relatively large anal shield]. Such complete data are fantastic for future research, but they also mean a lot more work processing these slides, as every slide has lots of unique data. I want to thank George Keeney, part-time curator of the acarology collection and a series of volunteers, Ben Carey, Rachel Hitt, Mitchell Maynard, Ben Mooney, Jake Waltermyer, and Elijah Williams, for their hard work in accessioning this material.


About the Author: Dr. Hans Klompen is professor in the department of Evolution, Ecology and Organismal Biology and director of the Ohio State University Acarology Collection.