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Photo#42331
Theory

Theory
Vero Beach, Indian River County, Florida, USA
February 6, 2006
Size: 3cm
OK, here is my theory: The dots outlined in green are the spiracles, as they are evenly spaced and uniform-looking.
The ones outlined in red are unevenly spaced and appear to be surrounded by melanized areas (an immune response). Perhaps the dots outlined in red are the exit wounds from the emerging larvae. Once again I chide myself for not collecting the caterpillar.

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What is this/these What is this/these What is this/these What is this/these What is this/these What is this/these Theory Theory

Moved

Moved
Moved from Braconid Wasps.

Could this be the work of two different parasitoids?
I've seen those black exit holes with silky residue (circled red here) on a hornworm in my yard, but with no evidence of the wooly cocoons your caterpillar is also carrying. See below

 
...
It is possible that the larvae emerged elsewhere and the hornworm moved of to try to feed. This caterpillar moved off after I disturbed it.
-Sean McCann
You can see some more of my photos at triatoma.blogspot.com

I agree
and I've seen this before. I took this shot this summer of the same basic behavior. The caterpillar in my shots was also very much alive and could crawl around. Why the heck the caterpillar stays there is a mystery to me. Maybe the wasps are releasing some kind of chemical that the caterpillars like?

 
Mystery?
Maybe because the caterpillar is sick and/or tired it doesn't move without some external stimulus to force it.

 
Polydnavirus?
Maybe it is an effect of the polydnaviruses that the wasps inject during oviposition?

-Sean McCann
You can see some more of my photos at triatoma.blogspot.com