While removing Italian Thistles (Carduus pycnocephalus) at Bernard Field Station volunteer workday, we noticed a number of leaves rolled up with webbing with these caterpillars were inside. When we were finishing up the workday, we found that this one had hitched a ride back to the lunch site on a volunteer's shirt. The student volunteers tried feeding it several types of leaves, which it didn't care for, but when we tried an Italian Thistle leaf, it chowed right down, eating a nickel-sized hole in no time at all. It's on the leaf in the photograph.

After perusing caterpillar photographs, I suspect this is a larva of a Painted Lady (Vanessa cardui), especially since the V. cardui larvae are sometimes called "Thistle Caterpillars". Here's another from LA County that looks similar:



Confirmation or correction will be greatly appreciated!