During a visit the day before, J showed me her lupine bush and asked me about these caterpillars. They totally grossed her out, because there were so many (~100?), all tangled in webbing. The best I could do on the spot was offer generalizations with comparisons to other gregarious and silky caterpillars, like western tent caterpillars and fall webworms. Curiosity got the better of me, so I asked her if I could take lupine clippings and caterpillars to raise, which I like to do from time to time, to find out which kind of moth they turn into. I didn't really need to collect any, because a simple internet image search "caterpillar eats lupine" got me an easy answer when compared to my photos. Eh, the adults don't excite me much; they're little brown jobs (LBJs) with snouts. Both the common names, Genista broom and Sophora, come from other preferred legume host plants. A couple bloggers I follow have also featured the Genista broom moth: Ohio Birds and Biodiversity (excellent comments about sightings) and Bug Eric. It's interesting to note we're seeing local caterpillars in October, versus spring and summer elsewhere. As for the specific bush lupine, this is my best guess based on J telling me hers has both yellow and blue blooms like those at Asilomar, a characteristic that I believe is distinctive in yellow bush lupine populations along the coast. And, I believe this phenomena is different than just the normal flower color change from yellow to purple after being pollinated. Being the nice friend that I am, I clipped off the remaining caterpillars and bagged them to save J from the ick factor. Her bush lupine is now only 2/3 its former size. It'll be fine.
