Collected and maintained on Birch.

A headshot at day 16 to compare with this headshot from day 22, after my pink highlighter treatment. A little increased reddish, but not much:

after 22 days I decided to try and replicate (with a little modification) an experiment I had read on the Cleft-Headed Looper. Apparently these caterpillars are generalists and change the color of their cutical to match the color of their surroundings DIRECTLY by sight!!

The study used green, brown, black, or white backgrounds and found that these cats could pretty much match those colors. A lot of pictures of these cats are reddish, though, so I thought I'd try to put one in a red-tinged environment and see if it would molt to be more reddish.

Unfortunately it was a very spur-of-the-moment thing and I'm afraid I didn't design my enclosure very well (pink highlighter on some paper taped to the outside of the plastic container). As you'll see in the next picture, this cat barely changed at all in a molt.

I would love to try this with properly prepared environments, and with more than one caterpillar.

The article I'm babbling about was:
Noor MAF, Parnell RS, Grant BS (2008) A Reversible Color Polyphenism in American Peppered Moth (Biston betularia cognataria) Caterpillars. PLoS ONE 3(9): e3142. doi:10.1371/journal.pone.0003142