Identifying a beetle from northern California
This is a long-horned beetle, family Cerambycidae; the site http://www.sbcollections.org/cbp/DB_Query.aspx?Field=family&amp;Value=Cerambycidae has a list of California species, with links to pages on each species (there are 387; not all species pages feature illustrations -- those that do figure museum specimens).  From that list the first that resembled your photograph is that covering Centrodera spurca (LeConte 1856), which has been found in Sonoma County; given that I haven't gone through the entire list there are likely other possibilities.

Centrodera spurca