An elegant living fossil…

In the insect world, hyperdiversity is the norm. More than a million species are known, and perhaps several million more await discovery. Beetles alone represent nearly a quarter of the earth’s described biota, with one genus (Agrilus in the family Buprestidae) bursting at the seams with more than 3,000 described species (Bellamy 2008). Biodiversity gone wild! While birders routinely field identify (and list) a majority of the birds they see to species, most insect enthusiasts are happy if they can simply identify their subjects to family—in most cases still leaving several hundred to several thousand possibilities for species identification. Even trained entomologists usually can identify only a tiny fraction of the insects they see and remain just as clueless about the vast majority of insects they encounter that don’t represent one of their limited number of study groups.

Pelecinus polyturator female | Wayne Co., Missouri

Pelecinus polyturator female | Wayne Co., Missouri

 Of course, that doesn’t mean field identification is impossible for all insects—certain groups such as butterflies, dragonflies, and tiger beetles lend themselves to field identification due to their relatively large size, bright colors, and distinctive markings. Many would also include the aculeate hymenopterans (i.e., “stinging” wasps and bees) among those groups for these same reasons. However, the vast majority of hymenopterans belong to a multitude of families characterized by tiny, parasitic species that seem (to this coleopterist’s eyes) to differ only in bafflingly minute details of wing venation and tibial spurs. (Honestly, I couldn’t tell you the difference between Tanaostigmatidae and Tetracampidae if my life depended on it!) Nevertheless, there are a small handful of parasitic hymenopterans in North America that are instantly recognizable due to their giant size (2 or more inches in length)—namely, Megarhyssa spp. (giant ichneumons) and the species shown in this post, Pelecinus polyturator (American pelecinid). Pelecinus polyturator is the only North American member of the family Pelecinidae, which itself contains only two additional species that are restricted to Mexico and Central/South America. It wasn’t always this way—fossils assignable to the family and representing 43 species in a dozen genera have been found as far back as the early Cretaceous (121–124 mya) across North America, Europe, and Asia (Grimaldi & Engel 2005). Surely this represents just the tip of the iceberg of Mesozoic and early Cenozoic pelecinid diversity, making today’s three species the last representatives of a once great lineage—”living fossils”¹ some might say.

¹ To ward off any scolding I might get from evolutionary purists, I get it; there is no such thing as a living fossil (except the T. rex skeleton in the movie “Night at the Museum”). I know that all species alive today have the same amount of evolutionary history behind them and are, if not from more immediate ancestors, highly derived compared to earlier life forms. I will admit that the term has become a bit overused as pseudoscientific shorthand for branding an organism as ‘primitive’ (another term which tends to raise hackles); however, I don’t see the problem with its use as informal reference to relatively ancient groups, usually more diverse in the past and now represented by only a few species. Innocuous shorthand is all it is.

This elegant female, recognizable by her extraordinarily narrowly elongate abdomen (males have a somewhat shorter abdomen that is widened at the end), was seen back in July 2011 as she flew to a blacklight and landed on nearby foliage in a mesic bottomland forest in southeastern Missouri’s Ozark Highlands. I have seen females on occasion over the years but have not yet seen a male, which are increasingly rare in more northern latitudes of the species distribution. I missed the focus a bit on this photo (and also the other half-dozen or so shots that I took)—photographing an active subject at night on elevated foliage without a tripod is difficult to say the least! Nevertheless, after post-processing it’s a decent photograph. If you are wondering why it took me so long to post it, that’s because only recently have I gained the confidence to “clean up” poorly exposed photos where the subject and/or substrate on which they are resting is so distractingly littered with debris as this:



Compare the original photo here to the final photo above it—how many post-processing tools can you detect the use of? 🙂


Bellamy, C. L. 2008. World catalogue and bibliography of the jewel beetles (Coleoptera: Buprestoidea), Volume 4: Agrilinae: Agrilina through Trachyini. Pensoft Series Faunistica 79:1–722.

Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects.Cambridge University Press, New York, xv + 755 pp.

Copyright © Ted C. MacRae 2013

More Eocene insects

Most of the Green River Formation (GRF) insect fossils that I have on loan clearly represent either beetles (order Coleoptera) or flies (order Diptera). I’ve already shown a few of the latter (fungus gnat, midge), as well as some that don’t belong to either order (ant, cricket?). Here are a few more that seem identifiable to order, but family-level identification is less certain. Thoughts from the readership would be most welcome.

This fossil shows an aggregation of insects that I believe represent some kind of beetle. Based on shape and size (16.7 mm length) I’m guessing perhaps either a diving beetle (family Dytiscidae) or whirligig beetle (family Gyrinidae). These are both aquatic families, although only the former is among the beetle families recorded from the GRF by Wilson (1978).

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There are two insect fossils on this specimen, but the closeup is the one near the center of the rock. It is tiny (3.5 mm in length), and at first I thought it might be a fly (order Diptera). However, dipterist Chris Borkent thinks it might be a small hymenopteran (bee?) because it has what looks to be long multi-segmented antennae. The only bee family recorded for the GRF by Wilson (1978) is Anthophoridae (now included within Apidae), of which this fossil clearly is not a representative. There are six other hymenopteran families recorded in that work, of which Tenthredinidae is the only one that seems plausible. Of course, it could represent a family not recorded by Wilson (1978). Collected along Hwy 139 in Douglas Pass (Garfield Co., Colorado).

Here is a closeup of the other fossil (far right in photo above). This looks to me like a brachyceran fly, and I’ve sent a high resolution version of the image to Chris Borkent to see what he thinks.

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The label accompanying this fossil indicates “Mosquito (?),” but to my eye this looks like a true bug (order Hemiptera). It is small—only 5.9 mm in length—and has the gestalt of a plant but (family Miridae) or seed bug (family Lygaeidae). GRF fossils representing the latter but not the former were recorded by Wilson (1978). Also collected along Hwy 139 in Douglas Pass (Garfield Co., Colorado).


Wilson, M. V. H. 1978. Paleogene insect faunas of western North America. Quaestiones Entomologicae 14(1):13–34.

Copyright © Ted C. MacRae 2012

The 2nd-oldest Known Myrmicine Ant

Among the 20 or so insects represented in the Green River Formation (GRF) fossils that I currently have on loan, this rather obvious ant (family Formicidae) is the only one that is firmly assignable to the order Hymenoptera (wasps, bees and ants). This is not surprising, as hymenopterans are not well represented among GRF insect fossils. In fact, of the 300+ insect species that have been described from GRF deposits (Wilson 1978), more than two-thirds belong to just three orders—Diptera (flies), Coleoptera (beetles) and Hemiptera (true bugs). Hymenoptera, on the other hand, comprise only 4% of GRF fossils (Dlussky & Rasnitsyn 2002). I presume these numbers are more a result of taphonomic (fossil formation) bias than a true reflection of insect diversity in western North America during the Middle Eocene (47–52 mya).

cf. Myrmecites rotundiceps | fossil impression from the Green River Formation (45 mya, middle Eocene)

cf. Myrmecites rotundiceps (length = 6.7 mm).

Ants in particular have been poorly represented by GRF deposits. Only four named species were known until Dlussky & Rasnitsyn (2002) reviewed available GRF fossils and increased the number to 18 (15 described as new, one older name placed in synonymy). Diagnoses, line drawings, and keys to all covered subfamilies, genera and species provide one of the best treatments to GRF insect fossils that I’ve come across. According to that work, the fossil in these photos seems comparable to the description and illustration given for Myrmecites rotundiceps, a unique fossil with the general appearance of ants in the subfamily Myrmicinae but differing from all known Eocene and New World fossil ants by its very short, two-segmented waist. The only difference I noted was size—6.7 mm length for my fossil versus 5.5 mm for the holotype (see figure below). Of course, I’m more comfortable identifying extant Coleoptera than extinct Formicidae, so I contacted senior author Gennady M. Dlussky to see if he agreed with my opinion. He graciously sent the following reply:

I agree that specimen on your photo is very similar to Myrmecites rotundiceps. It is larger (holotype is 5.5 mm long), but it may be normal variability. I cannot see another differences.

Myrmecites rotundiceps, holotype (Gennady & Rasnitsyn 2002)

Myrmecites rotundiceps Gennady & Rasnitsyn 2002, holotype (reproduced from Gennady & Rasnitysyn 2002)

If correctly assigned, M. rotundiceps is the second oldest known member of the subfamily Myrmicinae—the oldest being Eocenidris crassa from Middle Eocene Arkansas amber (45 mya). In fact, the only older ant fossil of any kind in North America is Formicium barryi (Carpenter) from Early Eocene deposits in Tennessee (wing only). [Edit: this is actually the only older Paleocene ant fossil—there are some Cretaceous-aged fossils such as Sphecomyrma freyi (thanks James Trager).] Since myrmicine fossils of comparable age are lacking from other parts of the world, this might suggest a North American origin for the subfamily; however, it could also be an artifact of incomplete knowledge of ants from older deposits in other parts of the world. Myrmicine ants make their first Eurasian appearance in Late Eocene Baltic amber deposits (40 mya) and become more numerous in North America during the early Oligocene (Florissant shales of Colorado, 33 mya). (Dlussky & Rasnitsyn (2002) consider the Middle–Late Eocene ant fauna to represent the beginnings of the modern ant fauna, with extant genera becoming numerous and extinct genera waning but still differing by the preponderance of species in the subfamily Dolichoderinae over Formicinae and Myrmicinae.


USA: Colorado, Rio Blanco Co., Parachute Creek Member.

The photo above shows the entire fossil-bearing rock (also bearing the putative orthopteran posted earlier).

My thanks to Gennady Dlussky and James Trager for offering their opinions on the possible identity of this fossil.


Dlussky, G. M. & A. P. Rasnitsyn. 2002. Ants (Hymenoptera: Formicidae) of Formation Green River and some other Middle Eocene deposits of North America. Russian Entomological Journal 11(4):411–436.

Wilson, M. V. H. 1978. Paleogene insect faunas of western North America. Quaestiones Entomologicae 14(1):13–34.

Copyright © Ted C. MacRae 2012

A 50-million-year-old midge

Several of the insect fossils collected from the Green River Formation (45–50 mya) that I am photographing appear to be flies, and specifically members of the “primitive” suborder Nematocera. This is not surprising, as the G.R. Formation of Colorado, Utah, and Wyoming, is composed of shales derived from volcanic ash sediments that were laid down in a system of large, shallow lakes. Most (all?) nematoceran flies are aquatic to some degree in the larval stage, thus the adults are also closely associated with such habitats for mating and egg laying.

Diptera: Chironomidae | USA: Colorado, Garfield, Hwy 139, Douglas Pass

Diptera: Chironomidae | USA: Colorado, Garfield, Hwy 139, Douglas Pass

This particular fossil looked to me a lot like the more elegantly preserved fossil of another fly that I posted a few days ago, which at the time I thought represented a member of the family Mycetophilidae (fungus gnats) or Sciaridae (black-winged fungus gnats). Several knowledgable specialists offered their opinions in comments at this site and at Facebook’s Diptera forum (my thanks to all who offered their opinion), with most settling on Mycetophilidae and Vlad Blagoderov further suggesting subfamily Mycetophilinae. The fossil posted here seemed to me to represent a dorsal view of the same species, but, of course, I’m a coleopterist—so what do I know? Indeed, dipterist Dr. Chris Borkent believes this is actually a species of Chironomidae (common name simply “midges”)—also a nematoceran but differing from Mycetophilidae by their longer front tarsi and longer, relatively narrower wings. Males of the family have thickly plumose (“feathery”) antennae, which are not visible in this specimen and thus suggesting it might be a female. I wouldn’t doubt Chris’ identification  for a second, as he comes from good stock—his father is Art Borkent, a world expert on several families of nematoceran dipterans. Art also agreed after seeing the photo that it looked like a female chironomid midge, so that is what I am going with. Thank you, Chris and Art, for your help in identifying this fossil!

Complete fossil specimen (63 mm x 52 mm maximum each axis).

Copyright © Ted C. MacRae 2012

An elegant Eocene fly


USA: Colorado, Garfield, Hwy 139, Douglas Pass.

Here is one of the more elegantly preserved specimens among the collection of Green River Formation fossil insects that I am photographing. It is obviously a fly (order Diptera), but I don’t agree with the preliminary identification of “Mosquito?” as indicated on its label. Rather, I think it is one of the fungus gnats—also members of the suborder Nematocera and, thus, closely related to mosquitos (family Culicidae), but with distinctly elongate coxae (bases of the legs) and lacking the elongated proboscis that mosquitos use for sucking blood. It’s hard to decide between Mycetophilidae (fungus gnats sensu stricto) or Sciaridae (dark-winged fungus gnats), which differ in whether the eyes meet above the antennae (Sciaridae) or not (Mycetophilidae). However, Borrer & White (1970) mention that species of the former are generally less than 5 mm in length, while the latter range from 5–10 mm. This specimen measures 4.15 mm from the front of the head to the tip of the abdomen, so  maybe that is evidence supporting Sciaridae (although perhaps there were smaller mycetophilids 50 mya than today).

Here is a view of the whole fossil, measuring approximately 50 mm on each side:



Borrer, D. J. & R. W. White. 1970. A Field Guide to the Insects of America North of Mexico. Houghton Miffton Company, Boston, 404 pp.

Copyright © Ted C. MacRae 2012

Beetle, orthop or something else?

I had such helpful participation with my first fossil ID request that I thought I would go to the well again. This one is not so enigmatic as the first—it is clearly an insect, but it’s the only insect fossil among the batch that I haven’t settled on at least an order-level identification. Again, this is one of a set of 20 fossils loaned to me by a local collector for photographs and possible identifications, all coming from the Green River Formation in Colorado and dating back to the early to mid-Eocene (45–50 mya).

USA: Colorado, Rio Blanco Co., Parachute Creek Member. Body length = 11.05 mm.

USA: Colorado, Rio Blanco Co., Parachute Creek Member. Body length = 11.05 mm.

The label for this fossil indicates “Planthopper; Homoptera; Fulgoridae”; however, the short, robust legs and overall gestalt do not look right for either a planthopper or really any of the other hemipteran groups. What I see is an indistinct (mandibulate?) head, a distinct and well-developed pronotum, mes0- and metathoracic segments that are not nearly as heavily sclerotized as the pronotum but also lacking any sign of wings, a distinctly segmented abdomen with 9 or 10 segments, and short robust legs. I’m thinking an apterous/brachypterous coleopteran (Staphylinidae?) or a wingless member of one of the orthopteroid orders (although size alone excludes many of the latter—at more than 11 mm in length it is too large for something like Zoraptera). At first I thought the extension near the apex of the abdomen was a cercus, but I now think this is part of the piece of debris over the abdomen as there is no evidence of a cercus on the left side—another knock against something orthopteroid. Still, the lack of any trace of elytra—however shortened—keeps me from fully endorsing Coleoptera. Okay, so what do you guys think?

Copyright © Ted C. MacRae 2012

Spider, insect or something else?

I recently received a batch of fossil insects from a local fossil collector, who is hoping that I and other local entomologists will be able to provide some level of identification beyond just “insect.” All are from the Green River Formation, a lake bed shale deposit dating back to the early to mid-Eocene epoch (45–50 mya). Most major insect orders and families were established and undergoing rapid diversification by this time, and as a result most of the fossils are clearly identifiable at least to order or even family. There is one fossil, however, that has got me stumped. The label that came with the fossil indicates “Spider (?)”, and while at first glance this is the first thing that comes to mind, the more I look at it the more I become convinced that it represents something else. What, however, I do not know.

The fossil is a cast and mold from a split rock, so two views of the fossil are available. I’ve photographed them to try to get a better look at the details and still can’t come to a decision (I’ve even considered a small crustacean or even a plant part). Perhaps somebody who reads this might have an idea?

Colorado: Garfield, Hwy 139, Douglas Pass. Maximum diameter = 22.5 mm.

Colorado: Garfield, Hwy 139, Douglas Pass. Maximum diameter = 22.5 mm.


Mirror half of same fossil.

Copyright © Ted C. MacRae 2012