Long, Black Wasp – American Pelecinid

2017 September 2

Here’s a very unique wasp that I found on the sidewalk on campus on August 28, 2017. It was very thin, really long (about the same length as my forefinger), and very, very black.


Sorry about the quality of the pictures, but “jet black” is a remarkably difficult color to photograph (plus, I only had my “pocket camera”, which isn’t quite as capable as my big DSLR).


As it turns out, this was extremely easy to identify. There is only one thing on BugGuide that even looks close. It is an American Pelecinid, Pelecinus polyturator. It’s a female, by the way. The males are a bit smaller, and also have a large bulge at the tip of their abdomen.


One feature that made the ID easy is that this particular species is the only member of its entire Family of wasps that exists in North America. From its appearance I thought at first it was one of the ichneumons, but no. This one isn’t even in the same Superfamily as the much-more-common ichneumons and braconids. These wasps are the last survivors of a particular lineage that used to be quite common and diverse back in the Mesozoic era, but is practically gone now. They are the sort of thing that used to be referred to as “Living Fossils”, although that term is kind of disparaged these days[1]. So, there is nothing else like them, and I can be unusually confident in this particular ID.

Anyway, the adults of these wasps emerge in the summer, and the females use that long abdomen to reach way underground, laying their eggs on beetle grubs (particularly June beetle grubs, the big, white, C-shaped ones that are commonly found when digging in lawns).

[1] “Living Fossil” implies that the organism is still identical to what is found in actual fossils, and that it has somehow remained unchanged for millions of years while the world altered around it. That isn’t really accurate, of course. These wasps are just as “evolved” as any other wasp, they have gone through as many generations, had as many random changes in their genome, and adapted to changing conditions as much as everybody else. It is just that all of their close relatives didn’t make it, so they kind of exist in splendid isolation from anything that really resembles them. As a result, their differences from other wasps are greater than their differences from their fossil ancestors, and so they *look* comparatively unchanged.

3 Responses
  1. Carole permalink
    September 2, 2017


  2. September 3, 2017

    Dang, how can we get some of those here? The blasted grubs eat my raised bed plants!

    They must have great chemical receptors to be able to target grubs underground. You’d think they’d be pretty well concealed by the dirt.

  3. September 4, 2017

    I’m pretty sure that the very long antennae help them find the grubs underground. Between them being essentially inside-out noses, and being very sensitive vibration sensors, they probably work very well for sniffing for the grubs, and then detecting the tiny sounds when the grubs slowly move around.

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