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:

Yuk!!!

Yuk!!!

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

REFERENCES:

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

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About Ted C. MacRae

Ted C. MacRae is a research entomologist by vocation and beetle taxonomist by avocation. Areas of expertise in the latter include worldwide jewel beetles (Buprestidae) and North American longhorned beetles (Cerambycidae). More recent work has focused on North American tiger beetles (Cicindelidae) and their distribution, ecology, and conservation.
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16 Responses to An elegant living fossil…

  1. 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!)

    Speaking from my own experience in wasp identification vs beetle identification: all I can say is, this is completely arse-about.

  2. sedeer says:

    That’s a lovely picture of a beautiful animal; well done catpuring it and good job with the processing! I also enjoyed your writing, particularly the aside about “living fossils” — it’s a shame that a useful term like that has so many incorrect connotations and associations…

  3. randomtruth says:

    You sure are good at making plants look healthy. Isn’t the acceptable term now “relic species?”

    • Yes that’s a perfectly acceptable term. I’ll use that next time I try to get a lay person interested in natural history… and watch their eyes roll back into their head from boredom! Scientists wonder why they have trouble connecting with non-scientists – insistence on use of dry, technical terms such as “relict species” is one of the reasons. There’s a time and place for pedantics, but science outreach is not one of them. I’ll stick with “living fossil” and make sure nobody takes it to mean that rock impressions can actually come back to life.

      p.s. – not a rant at you, but rather the evolution hulks that prowl the internet looking for wrongness.

  4. Jon Quist says:

    Nice. If there werent a such thing as Beetles, Hymenoptera might be my main focus.

  5. gergrd says:

    We use to see these frequently in the summer when I was (supposed to be) growing up in Michigan and Ohio in the 50′s and 60′s. My parents told us that they would land on your face and sew your eyes shut with that long tail. Needless to say, we steered clear of these evil creatures! Since I’ve returned to the east (Virginia) over twenty years ago, I’ve looked for a pelicinid, but have never encountered one. I don’t know if they just don’t range to this area or if they’ve been wiped out. Anyway, cool creatures and nice to see your photo.

    • They are said to parasitize white grubs (larvae of June beetles that live in the soil and feed on grass roots); however, adult females are usually found in forests, particularly where there is abundant dead wood – not typical habitat for phytophagous white grubs. Because of this it has been suggested they actually parasitize beetle larvae living in decaying wood. At any rate, forest habitats in mid-late summer are the best place to look for them.

  6. Chelydra says:

    I was pleased to come across multiple females in one day this summer, in an oak-pine forest in northern lower Michigan. In hindsight, given how active they were, I should have observed for a while longer in hopes of seeing either oviposition or males. Nitpick – if there’s a second Pelecinus native to Mexico, P. polyturator isn’t the only North American species. Looks like it was regarded as monotypic until 1999, hence the confusion.

    • I would love to see one of these ovipositing!

      Yes, it would have been more correct for me to say “North America north of Mexico” or “the U.S. and Canada,” but on this blog I tend to use the terms “North America” and “Central/South America” as rough equivalents for the Nearctic and Neotropical realms. I did mention the occurrence of another species in western Mexico and a third in Central/South America, so technically there are three “North American” species.

  7. macromite says:

    I haven’t seen a Pelecinus polyturator in years, but can still conjure up an image of one flying around a porch light more than 40 years ago. Excitingly interesting for a hymenopteran, but pretty messy when it came to fitting a pinned specimen into a cigar box, if I’m remembering correctly.

    In the scientific literature, I think it behoves authors to try and avoid cultural pitfalls like ‘primitive’, but the same people that rant and rave about primitive use terms like ‘native’ as if they were perfectly objective and dozens of other loaded words that obscure what is actually going on. Being selectively pedantic is useful if one wants to feel superior, but pretty callow overall. After all, ‘primitivus’ simply means first or early in Latin, and if something looks like it came before most of the similar animals or plants we are used to, primitive seems a good word to get that feeling across.

    • I’ve got a few pinned specimens from years ago. A row of them looks pretty spiffy as long as the wings and legs are tucked close to the body.

      Your point is spot on. I think we should give science outreach authors – whether they be popular science reporters or bloggers – a little latitude with word usage and save our criticisms for the actual scientific manuscripts that come across our desks.

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