Upon returning to the Frost from lunch yesterday, I noticed a little hymenopteran hitchhiker clinging to my shirt – a female trigonalid wasp!
Apparently these are pretty rare wasps, and the reason for that is their remarkable life cycle:
- Large amounts of minuscule eggs are laid at the edges of leaves, accomplished with a pretty strange abdomen.
- The eggs hatch when they are eaten by a caterpillar (in this case, a saturniid or arctiid)
- Once inside the caterpillar, the wasp larva survives only if the caterpillar is already being parasitized by another wasp, like an ichneumonid. The trigonalid larva proceeds to parasitize the other parasite (hyperparasitism!)
- If the caterpillar isn’t already parasitized, but gets chewed up by a vespid or potter wasp to be fed to it’s own larvae, the trigonalid larvae will parasitize that larvae.
There was only one trigonalid specimen in the Frost (at least where they should be in the collection), and it’s a male Orthogonalys pulchella collected in State College in 1982… now we have two!
Now to change gears to our collecting trip back to Ten-Acre Pond on Monday: I spent much of it with a D-frame net in hand searching for some aquatics, specifically a water scorpion (one of my favorites). And, somewhat unexpectedly, after a long time dip-netting, I got one!