I'm adding these images to clearly document the presence of T. flavolimbata gathering on Symphytotrichum chilense (=Aster chilensis).

The principle host for T. flavolimbata is Coyote Brush (Baccharis pilularis), but I have photographed it feeding on Baccharis douglasii and seen it, as here, on Aster chilensis...mostly in small numbers, but a few times in somewhat larger numbers (about 10-15?). I have not yet seen T. flavolimbata actually feeding on Aster chilensis, though in one instance I vaguely recall leaf damage on a plant they were on. Hogue (1970)(1) lists two collection records on A. chilensis, and this 1986 paper mentions that in a laboratory experiment:

"An adult was observed to feed continuously on A. novae-angliae, [and] larvae were able to complete their development after substantial feeding on both A. novae-angliae and A. alpinus..."

The similar looking species T. labrata also uses Baccharis pilularis as a host plant (as well as Ericameria ericoides). T. labrata differs from T. flavolimbata in having very large pronotal spots, and elytra less pubescent and more brilliant green. But those characters can be variable in both T. flavolimbata and T. labrata...borderline cases can best be resolved by examining terminalia (the tip of the aedeagus in flavolimbata is abruptly triangular, while in labrata it is gradually tapered). T. labrata is mostly recorded/known from Santa Barbara County north to Monterey and southern Santa Cruz Counties.