Found at UV light on a warm night (daytime high in San Francisco around 80 F, ambient T about 65 F at time of collection, little to no wind), collected into ethanol. I thought this was a small crane fly in the field, so was very excited and surprised to see that the wing veins and other features seem to match Dixidae! My only worry is the possible presence of minute ocelli on the vertex above the antennae and between the compound eyes, but perhaps it is an artifact. The first flagellomere looks cylindrical and I don't see katepisternal setae, so genus Dixella?

Wirth and Stone (in the Aquatic Insects of California) list aliciae, californica and somnolenta, but I don't have access to Nowell 1951 or Peters and Cook 1966 (but I've now ordered the latter).