Hi there- I was doing some field work in Nogales, Arizona (Santa Cruz County) and came across this caterpillar. There was a large group of them scattered among 3-4 oak trees. I unfortunately know little about insects, and was not having much luck identifying the species by comparing my pictures to ones on-line. I was hoping that you could help me identify these critters. They were an orangey-red color with black protuberances. I did not see them in any other tree besides the oaks and when they weren’t eating the leaves, they were bobbing from side to side. Thanks.
This looks like a Spiny Oakworm in the genus Anisota.
Ed. Note: (11/21/2005) The following correction just came in from Jim Tuttle.
I enjoy scrolling through your website periodically, and from a practical point of view I am always looking for interesting records, food plants, and range extensions for the Sphingidae, although I always take notes of the Saturniidae too. Good job, it is a useful tool for the nature lover or the frantic gardener. I casually noted two id’s that need correcting. Spiny Oakworm 10/18/2005 is actually Anisota oslari. Keep up the good work!!