American Pelecinid Wasp

Today’s PEI animal is a good example of why you shouldn’t judge a book by its cover. This ominous-looking insect is the harmless and beneficial American Pelecinid Wasp (Pelecinus polyturator, photo by Michele MacKinnon used with permission).

Photo: An American Pelecinid Wasp (Pelecinus polyturator) on PEI. Photo by Michele MacKinnon, used with permission.

You can be forgiven if you didn’t immediately recognize this as a wasp. It doesn’t sport the yellow-and-black stripes we usually associate with this group, and it may remind you a bit of a scorpion. (These wasps are sometimes called Scorpionflies, although that name is more appropriately used for another, unrelated insect). However, a close look reveals the thin waist between thorax and abdomen characteristic of wasps.

That dangerous-looking hind end isn’t a giant stinger, it’s the female’s abdomen, modified into an ovipositor for laying eggs. The wasp uses that ovipositor to poke into the ground until she hits a June Bug grub (larva). She’ll then deposit a single egg on the grub, and when it hatches it will feed on and kill the June Bug. If you don’t appreciate grubs killing your lawn, thank the American Pelecinid Wasp for her services!

Only females have that long ovipositor, and you’re unlikely to encounter a male in North America: entomologists estimate that only about 2-5% of our Pelecinid Wasps are male (though the South American population has a more typical male-to-female ratio).

While these insects can breed in the usual way, they are more likely to reproduce via parthenogenesis, in which a new female wasp is produced from an unfertilized egg. (These offspring are clones of the mother, and so always female). While that may seem strange to us, it isn’t that uncommon in nature. Parthenogenesis has been documented in plants, invertebrates, amphibians, reptiles, fish, and birds.

American Pelecinid Wasps pupate and emerge from the soil mid-summer. Adults feed on nectar – picking up pollen as they do – and so provide pollination services in addition to pest control. Late summer and early fall are the best times to see American Pelecinid Wasps, as females fly slowly over the ground seeking out June Bug larvae to lay their eggs. How they detect the grubs is unknown, but the wasps are successful enough that it’s not uncommon for June Bug researchers collecting larvae to end up with Pelecinid Wasps instead!

If you think Pelecinid Wasps look a bit pre-historic, you’re not wrong. They’re the only living members of their family (Pelecinidae), with fossilized ancestors dating back 165 million years. The wasps have changed very little over this time, although females are a bit larger now than historically – natural selection seems to have favoured a longer ovipositor.

Catch an American Pelecinid Wasp and she may try and poke you with her ovipositor to defend herself but has no venom and can’t sting. Even so, it’s best to let her be and just enjoy watching this native and beneficial member of PEI Untamed!