Is this a “Banded Alder Beetle”?
I took this photo while backpacking in the East Fork of the San Gabriel river of southern california 2 weekends ago (7/30/05 to be exact). After some web searching, it appears to be the “Banded Alder Beetle” although the marking aren’t exactly the same. Also, this particular area exhibited much forest devastation due this past winter’s record rainfall and storm damage so i’m figuring they’re feeding on the “dead alders”… Do you agree?
There is always some degree of individual variation in the markings within a species. This is a Banded Alder Borer, Rosalia funebris, and the markings are very similar to the photograph in our copy of Hogue’s Insects of the Los Angeles Basin. The larvae feed on dead wood of a variety of hardwood trees including alder and ash as well as occasionally eucalyptus and live oak. They are also sometimes attracted to paint fumes. Your theory is possible.