I encountered this beautiful moth on Bodega Head today, 1 October 2012. Hard to miss those attractive sinuous gray markings bordered in black and the legs striped with black, white, and gray.
Here's a view of the dorsal (upper) surface.
There were two long white and gray antennae on the head, and dramatic spots and stripes on the thorax.
After taking these photos I checked online and found a likely candidate — the Painted Tiger Moth (Arachnis picta). They're supposed to have red hindwings, a feature I hadn't looked at the first time.
So Michelle came back out with me and assisted in gently moving the forewings to expose the hindwings below. The moth became active and started vibrating its wings. (Insects often do this to generate heat in order to fly.)
This view helped confirm the identity. Note the dragon red color on the hindwings and at the base of the forelegs. When insects have bright colors like this, it's often a warning signaling their toxicity to potential predators.
When the moth crawled to the edge (just before it flew off), the abdomen was also revealed. Bright orange with gray and black spots!
What a way to start October!
Painted Tiger Moths are found from central California through the southwestern United States to western Texas. Adults fly in late summer and fall. Caterpillars feed on legumes such as lupines (Lupinus spp.).