What kind of caterpillar is this? Another one
I found this one near our door, so I have no idea what the host plant is. He was all fuzzy.
This appears to be some type of tiger moth caterpillar (family Erebidae, subfamily Arctiinae), which are somewhat characteristic in having the long, dense hairs all over the body. We have a large number of species of tiger moths in California, but from what I can see in the photo, I think it might be Estigmene acrea, the Salt Marsh Moth.
Despite its name, the Salt Marsh Moth actually occurs throughout North America, including the vast interior, far from any salt marshes, though it does occur in the latter habitat as well. When its wings are folded, the moth appears solid snow-white (with a few black flecks) from the dense scales and hairs on the fuzzy body and front wings; when the wings open, however, the orange abdomen and hind wings can be seen! This is a showy animal. See an example here: https://bugguide.net/node/view/1743636/bgimage
What would help solidify the ID of this caterpillar would be a shot of the head, especially the front; if it's what I suspect it is, it will have a black head with a yellowish stripe down the center and a yellow "upper lip": https://bugguide.net/node/view/1057151. Please let us know if you get another chance to observe one!
Schlinger Chair and Curator of Entomology Matthew L. Gimmel, Ph.D.