Pink and Green Caterpillars on Desmodium - Atomacera debilis

Petre et al 2007

Thank you everyone for the fantastic info. I have updated my field notes. Since you were kind enough to identify the creatures for me, I was able to read an article online that describes the defense mechanisms that Natalie mentions, including toxins, repellants and hairs. If I understand correctly these become more concentrated as a larva advances to later instars, and at the same time the coloring becomes aposematic. How cool to have such a fascinating bit of nature in our yard! Since there are so few photos of the species, I'll post the other two photos I have, they are of earlier instars, and they are much less conspicuous than their older siblings here.

… Sara Tangren, 25 March, 2011 - 8:06pm

Moved

Moved from Unidentified Sawfly Larvae.

… Charley Eiseman, 24 March, 2011 - 8:34pm

Argidae

These are larvae of the sawfly Atomacera debilis Say. From the little bit written on them, they feed on Desmodium in groups of 5 or 6. The only thing written on the pink one is that some are pink or with a red tinge " .. these being mature or nearly so."

… Dave Smith, 24 March, 2011 - 8:21pm

Moved

Moved from ID Request.

… John R. Maxwell, 24 March, 2011 - 4:12pm

They seem to be sawfly larvae...

The 1979 Catalog of Hymenoptera (1) lists just two sawfly species that feed on Desmodium: Atomacera debilis and Sphacophilus apios. These don't look like larvae in either of those genera to me, based on images on BugGuide. It will be interesting to see what Dr. Smith says.

… Charley Eiseman, 23 March, 2011 - 10:05pm

These do remind me of Atomacera decepta.

Especially with those protuberances on each body segment that seem to be exuding something. See the little droplets? I'm assuming its something that is supposed to scare us off or warn the other larvae.

These could just be earlier instars and thats why they don't resemble what we have on the guide which all seem to be later stages. They may feed on Desmodium but it just hadn't been observed in 1979 or they could be Atomacera debilis, of which there are no larval pictures of here on the guide. Members of the same genus can be quite different in appearance.

… Natalie Hernandez, 24 March, 2011 - 3:53pm

and

why is one pink?

… Sara Tangren, 23 March, 2011 - 8:09pm