Campoplegines, Part 3

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.

An older, and apparently unparasitized, spicebush swallowtail caterpillar.

About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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3 Responses to Campoplegines, Part 3

  1. Dave says:

    Good thing we share a common ancestor with birds, or we’d probably have failed to recognize all these amazing costumes as anything of interest. Imagine if we shared a closer common ancestor with a cephalopod – what would we see? Even now some people don’t believe in defensive mimicry, they think it is more in the mind of the beholder. Some skepticism is a good thing, but not with so many convergent examples of similar effects.

  2. Marvin says:

    Great series. Interesting and informative. A fascinating part of nature few people see or know anything about.

  3. Pingback: » Monday links

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