Following up on Joyce's post of a (remarkably!) gravid female on Baccharis douglasii...here are photos of an adult actually feeding on a leaf of B. douglasii. This is of interest because the host plant for T. flavolimbata is generally known to be the more widespread and abundant B. pilularis (aka "Coyote Brush").

This image was photographed at the same locale as Joyce's, which is a wet site adjacent to a coastal creek estuary. "(Salt) Marsh Baccharis" is a common name for Baccharis douglasii glutinosa, and there is B. pilularis growing nearby on drier substrate. The references I've seen refer exclusively to B. piluaris as the host for T. flavolimbata, but Rob Westerduijn remarked on a past Trirhabda post that chrysomelids will often utilize more than one species within a genus. Marsh Baccharis is not nearly as common a plant as Coyote Brush, and it would be interesting to see if they are both used by T. flavolimbata at other sites where they co-occur.

PostScript (1/2/12): I've learned more since the initial post here...for host plant details, see "Food" entry on the info page.
Note: There's been a name-change: what was referred to as B. douglasii in 2009 now goes by B. glutinosa.