Fossils – a look into the past


Parasitic wasps in amber (above). These specimens have been studied and some are deposited at the Triplehorn Insect Collection.

No one really knows the number of insect species that have been formally described and named, but it is surely a six-figure number.  Of these, some will sure turn out to be duplications, but beyond that, the consensus opinion is that the real total number of different kinds of insects in the world is in the millions or tens of millions (and some think it may be even higher).  That leaves a lot of exploration, discovery and documentation left to do, the first two of those being the “fun” parts of insect taxonomy.

If those numbers are not not impressive enough, consider that the estimates only include insect species that are alive today! Most paleontologists (the scientists who study fossils) will tell you that the number of ‘extant species‘ (same as living species) is but a tiny fraction of all those that have ever existed on Earth.

Despite the fact that we taxonomists already have a monumental task in front of us with just today’s species, we also tend to investigate fossils as well. Why? Because they provide precious insight in the evolution of insects and help inform our research of the living groups.

Until recently the Triplehorn Insect Collection did not have any fossil specimens in its holdings. That’s partly due to our history — the collection is a reflection of the interests of previous curators, faculty and students associated with it, and their focus was in extant species.  It’s also partly due to the chronic lack of storage space that plagued our collection for so many years.  Another big obstacle is the fact that keeping fossils adds a whole new level of complication to our already complex curatorial task.

All that aside, my research interests, and those of my students and collaborators, led us to take a determined step into the past. As the current caretaker of the Triplehorn collection, that meant the addition of fossil insects to our roster. We started creeping into this new adventure slowly.  It began some 15 years ago with a colleague in Germany who is deeply interested in the insects embedded in amber, and in particular, Baltic amber.  He would sort specimens of parasitoid wasps of the group we are currently studying and offer to sell them to us.

Amber from the area around the Baltic Sea has been known since the Stone Age and was used both for jewelry and medicine.  Pieces were either collected along the shores or, later, actively mined in countries stretching from Denmark in the west to Russia in the east.  This is a huge area, and the deposits occurred over a long period of time.  The age, actually really the ages, of Baltic amber range from roughly 40 to 60 million years.  The amazing thing, for our purposes, is that insects, mites, and other small organisms would get caught in the sticky tree resin and be preserved for the ages.  In a good specimen it feels like you’re looking at something that was just collected yesterday, with all the smallest details of hairs and body texture perfectly preserved.  In fact, though, there’s usually very, very little of the original specimen left, and what we see is merely the cast of its body.

We began to slowly acquire amber specimens of the minute parasitoid wasps we study (order Hymenopera, family Platygastridae) and deposit them in the Triplehorn collection.  Slowly, not because these inclusions are particularly rare, but because they’re not cheap.  We now have several hundred of these, from which we’ve described a few new species and one new genus (Cobaloscelio Johnson & Masner in Masner et. al. 2007.)  On a global scale our collection is small and specialized.  Much, much larger collections with amber from many other places around the world may be found in, for example, the Museum of Comparative Zoology, the American Museum of Natural History, and the State Museum of Natural History in Stuttgart, Germany.

[Just as a historical side note, the main collection of Baltic amber used to be stored in the Zoological Museum in the city of Königsberg in Germany. This city is now known as Kaliningrad and is located in a small piece of Russia on the Baltic coast, otherwise surrounded by the country of Poland. Unfortunately, this museum and almost all of its contents were destroyed by bombardment during World War II.]

In the past few weeks we’ve graduated from our own small niche of amber wasps. This began when Ohio State’s Orton Geological Museum decided that they needed to make more space for dinosaur bones. Their solution was to find a new home for some of their fossil insect specimens. (Can you imagine prioritizing dinosaurs over insects? Neither can I.)  We decided that it was most appropriate for the material to stay at Ohio State, and so the Triplehorn collection is now the proud owner of hundreds of specimens of Green River Shale insects.

Moving the Green River Shale cabinets and drawers was strenuous work. Soon we’ll start the cataloguing process.

Fossils from the Green River formation are comparable in age to Baltic amber, but we know that number more precisely: 53.5 – 48.5 million years. And we’re no longer dealing with amber, but with rocks. There are three main deposits of Green River shale made up of the sediments that were deposited in mountain lakes near the present day area of the Uinta Mountains in Utah. They’ve been known to Europeans since the explorations of the West in the first half of the 19th Century, and the fossils are very well known. In fact, if you go to a natural history shop that sells fossils, it’s likely that some of the amazing fossils of fish you see come from the Green River deposits. The best areas for fossils were made from fine mud deposits. In those, the very small details of insects and spiders are preserved. Unlike amber though, these fossils are compression fossils, specimens that have been pretty much flattened by tons of sediments sitting on top of them.

Fossil Butte 2015.jpg

Fossil Butte National Monument in Wyoming. Not the kind of habitat where we’d normally be looking for insects!

The adoption of this collection will call for skills and expertise beyond those typical of a collection of dried insects. One thing we won’t have to worry about are “museum pests,” insects like carpet beetles that will feast on all sorts of dried organic matter such as the bodies of dead insects. Instead, we need to take into account the pure dead weight. These fossils are, after all, embedded in rocks. Handling hundreds of pounds of stones will surely put a premium on strong, athletic undergrad student assistants in the future!

Our tasks ahead are, first, using the records of the Orton Museum, to determine as precisely as we can the area(s) within the Green River Formation that these specimens were collected.  Then we’ll use our existing connections as well as the Fossil Insect Collaborative, to let paleoentomologists (entomologists specialized in the study of fossil insects) know that these materials exist and are available for study.  We need their help because, while we can distinguish beetles from flies, they are the ones who can figure out exactly which species of beetle or fly is in a particular fossil.

I have a colleague, recently retired, who always emphasizes that fossil collections add the critical dimension of “deep time” to our understanding of biodiversity.  With this new acquisition then, we hope to make a contribution to that understanding.  Along the way we’ll certainly learn a lot about paleontology and the curation of fossil insects.

Here’s a list of our work with Baltic, Canadian and Lebanese amber over the last several years. The Canadian and Lebanese materials are much older than Baltic amber, by about 80 million years! Some species and one genus were described based in part on specimens in the amber collection at the Triplehorn Insect Collection (photos, top):

Johnson, Norman F., Lubomir Masner, and Luciana Musetti. 2008. Review of genera of the tribe Sparasionini (Hymenoptera: Platygastroidea, Scelionidae), and description of two new genera from the New World. American Museum Novitates 2629: 1-24. (available online here)

Johnson, Norman F., Luciana Musetti, and Jens-Wilhelm Janzen. 2001. A new fossil species of the Australian endemic genus Peradenia Naumann & Masner (Hymenoptera: Proctotrupoidea, Peradeniidae) from Baltic amber.  Insect Systematics & Evolution 32: 191-194.

Masner, Lubomir, Norman F. Johnson & Andrew Polaszek. 2007. Redescription of Archaeoscelio Brues and description of three new genera of Scelionidae (Hymenoptera): a challenge to the definition of the family.  American Museum Novitates 3550: 1-24. (available online here)

Johnson, Norman F., Luciana Musetti, and Lubomir Masner.  2008. The Cretaceous scelionid genus Proteroscelio Brues (Hymenoptera: Platygastroidea).  American Museum Novitates 3603: 1-7. (available online here)


About the Author: Dr. Norman Johnson is Professor of Biology and Entomology with appointments in EEOB and Entomology. He’s also the Director of the Triplehorn Insect Collection. Norman works with minute, but crucially important, parasitoid wasps. You can learn more about his work by visiting the website of the Johnson Lab.