Their caterpillars eat many many plants but do the most crop damage to beans and cotton. Favorite caterpillar foods include anything in the pea family (Fabaceae), mallows Malvaceae and Malva), beans (Phaseolus), clovers (Trifolium), and cotton varieties Gossypium).
Shady Oak Butterfly Farm posted a photo of the pink caterpillar on their Facebook page today. http://www.facebook.com/#!/ShadyOakButterflyFarm
I've had hundreds of Gray Hairstreaks in our garden over the years and I have yet to see a pink caterpillar. I will be positively vigilant this coming butterfly season!
Their flights are May-September in the north and in the south they have three-four flights from February-November.
for a table of more caterpillar foods.
The page was photographed and compiled by Peter J Bryant, Dept. of Developmental and Cell Biology, U.C. Irvine.
If you are in the mood to poke around a bit more, the state of Ohio
has a cool page "Species A to Z Guide" at