I’ll conclude Campopleginae Week with this cocoon I found on a spicebush (Lindera benzoin) leaf in September:
The host plant and the big fake eyes on the caterpillar skin identify the ichneumon’s host as a spicebush swallowtail (Papilionidae: Papilio troilus).
The 1979 Catalog of Hymenoptera doesn’t list any swallowtails (Papilio) as hosts for campoplegine ichneumonids. I find only two ichneumonid genera that have been reared from swallowtails: Trogus (Ichneumoninae), which emerges from chrysalises, and Meochorus, which is a hyperparasitoid (i.e., parasitizing another wasp, possibly a braconid, that parasitized a swallowtail caterpillar). Since this cocoon was already empty, I’ll have to look for one earlier in the season and collect it to find out what campoplegine is responsible. The plainness of the cocoon narrows down the options, and Bob Carlson said the dimensions of the cocoon “might help to discern whether it was made by something like Hyposoter versus something like Dusona.”
So, to review, the defense strategies in campoplegine cocoons include being dangled from a thread, making them harder to get at; having the ability to jump around, possibly thereby avoiding predators; bearing a resemblance to bird droppings, thereby looking less like a meal; wearing the host caterpillar’s skin as a protective covering; spinning a false cocoon on the outside of the host caterpillar, making it look like the caterpillar has been abandoned; and in this case, choosing a host caterpillar whose skin both resembles a bird dropping and has scary fake eyes. This last strategy is reminiscent of that of the braconid wasp Dinocampus coccinellae, which spins its cocoon under its ladybug host, taking advantage of its warning coloration.
Now, if I just devote one week to each subfamily of ichneumon wasps, I could have them all covered by the end of August! Or I could cover one of the described North American ichneumonid species each day for the next 14 years… another 8 years or so for the ones that don’t have names yet. With this kind of diversity in parasitoids, you can see why it has taken me 84 posts to even mention a butterfly.
Edit, 11/6/2019: I got a note from Ansel Oommen, who found five parasitized spicebush swallowtails like the one I found and reared five adults. He sent them to David Wahl, who said:
All specimens are the same species of Hyposoter. There are 27 described Nearctic Hyposoter, with probably 3-5x that number in total. We have about 13 spp. identified to species by Townes and others, none of which match your species. It seems to be the same species as a morphospecies segregated by Townes (sp. 116) but it doesn’t perfectly match.