Many caterpillars munch on plants which are highly toxic. For instance, the Tobacco Hornworm Manduca sexta can be found lunching on practically anything in the Nightshade family Solanaceae. Which includes: tobacco, petunia, tomato, pepper, potato, nightshade, etc. M. sexta can sequester these poisons and be unaffected itself. However, these plant poisons in the caterpillar's body don't stop the Microgastrinae wasp Cotesia congregata from turning the hapless caterpillar into an incubation chamber. Why? Are Microgastrinae unaffected by alkaloids, period? Or are they affected by some and not others? There are many different species of sphinx most of which are named after their different plant hosts. Does knowing the caterpillar's preferred food plant tell us anything about which wasps or even which tachinids will use it as a host?

Is the Catalpa Sphinx Ceratomia catalpae is really parasitized by the Cotesia congregata wasp? Or do plant alkaloids matter? The fact that the wasp cocoons are larger and fewer in number than those seen on M. sexta makes me wonder if it is indeed a different species of wasp. There is vast difference in width between these two varieties of Sphinx caterpillars. Is this difference in mass a superficial difference only? Or does it affect the choice of parasite? For that matter C. catalpae. is much skinnier than most of the other Sphinx caterpillars which makes me wonder if it shares less genetic material in common with the other members of the Sphinx family.

Take the challenge and raise the wasp cocoons from C. catalpae or some other variety of sphinx caterpillar to see if they do indeed turn out to be Cotesia congregata or some entirely different species or genus of parasitic wasp.

Here is a helpful resource that has been the work of our own project member Jose Fernandez-Triana and his colleagues. In his own words:

I am taking this opportunity to let you know that yesterday it was published a large checklist on the world species of Microgastrinae. It is open access and can be freely downloaded here:
https://zookeys.pensoft.net/article/39128/

Although is a technical document, it contains picture of all genera of Microgastrinae (although from dead specimens in collections) but it also have some initial sections where the group is explained and details on host biology are also briefly discussed. I thought that might be of interest to you and your team, and because the paper is free to access, feel free to pass the info to whoever might be interested.

Cheers,
Jose

I plan to refer to this myself to learn even more about these mysterious braconids. I appreciate the diligent research and years of study this list represents. Thanks so much! Noelle Congdon