This bug was noticed by Joyce Gross on 10/11/13, as it crawled inside a ziploc bag containing galled twigs of Epilobium canum that I'd collected a few days earlier on 10/6/13 from Del Puerto Canyon.

After quickly snapping and viewing this photo, I recognized it as Pronotacantha, which I had seen earlier in the year at Kelso Dunes in the Mojave Desert:



I was surprised to see this desert species (known from CA and AZ) coming from Del Puerto Canyon, but Joyce pointed out that the habitat there is quite arid, and there are various plant species with Mojavean affinities that range along the arid corridor of the inner Coast Ranges at the west edge of the Central Valley...extending up to the eastern Diablo Range, where Del Puerto Canyon lies.

I'm presuming this is Pronotacantha annulata (though apparently there is one other US species, P. concolor, described by T.J. Henry in 1997). I wonder if there are any other records of either species this far to the northwest?