I have been unable to identify this caterpillar I found on the underside of a jade plant. Can you please tell me what it is?
What we’re looking at in this photo is actually an adult female moth emerging from a cocoon. This is a strange species called the Western Tussock Moth (Orgyia vetusta), whose females have no wings! The blob-shaped thing with the lighter “fur” is the female moth, whose antennae and legs are tucked enough to not be visible, and the darker brown thatch-like structure she’s hanging from is the cocoon. Note that the cocoon incorporated the bristle-like dark hairs from the distinctive-looking caterpillar who constructed it. In this species, once she’s finished pupating, the flightless female emerges from the cocoon, then stays on it as she releases her pheromones, attracting the (winged) males to her to mate.
Collection Associate Sandy Russell reports that she has seen adult males of this moth in numbers recently at her moth-attracting light station in the Santa Barbara foothills, so the timing of this female’s emergence makes sense.
You can see photos of both the caterpillar and adults of both sexes (including an alternate view of the female), as well as read more about this species, in this Ask a Curator post. For even more information on and photos of this species (and its parasitoids!), see this excellent page by Joyce Gross of UC Berkeley.
Schlinger Chair & Curator of Entomology Matthew L. Gimmel, Ph.D., and Collection Associate Sandy Russell