It looks like a fire fly.

I hate to disagree, but this doesn't look like any of the fireflies that we have here. It looks more like some type of soldier beetle to me. I could be wrong, though.

Over 100 species of soldiers beetles in California, generally beneficial.

http://cesanjoaquin.ucdavis.edu/index.cfm?blogpost=4562&blogasset=28896

Thanks, I guess it is easy to look them up on the web once you know their name. Hard to look up by picture.

Glad to hear they aren't eating my trees.

I'm no Entomologist but that photo still looks like a firefly.

http://www.lizchristygarden.org/lcbh_files/FIREFLY.gif

I suppose all bugs look alike, but these aren't fireflies. Pretty sure the soldier beetle ID is correct.

Fireflies have black&white striped antennae; black head and large black eyes; wide thoracic shield with dark patch above; smooth white-lined wing covers; wide light-producing body segments compared to other segments.

On the soldier beetle above, all body parts are orange; eyes are small and beady; thorax is narrow; wing covers are leathery and all dark; all abdomen segments fairly equal.

Fireflies are also not found in Norcal mostly east coast to Midwest https://www.mos.org/fireflywatch/range_maps

Looks like the soldier beetles I see on my trees.