According to Evans & Hogue in their book Field Guide to Beetles of California:
"Like Eleodes, Coelocnemis species stand on their heads and emit defensive secretions from the tip of their abdomen. Members of this genus are readily distinguished from Eleodes by possessing two rows of fine, golden brown hairs on the lower half of the inside margin of the hind tibiae."

I noticed that there weren't really any photos currently in BugGuide that showcased this feature, so I thought I would upload these images in the hopes that they would provide a good means of illustrating this diagnostic trait. I had rescued this beetle from the landlord's pool and (as is often the case) it initially appeared quite deceased and was in the typical belly-up position. It did recover after warming up and drying off a bit, but I was able to get these close-up shots while it was still in a somewhat comatose state.

I'd like to take a moment to mention that although Evans & Hogue only specifically mention the presence of these golden hairs on the inside margin of the hind tibiae, it has been my observation that the same feature occurs on the tibiae of all pairs of legs. I am uncertain whether this is true of ALL Coelocnemis species or just the common species I so regularly observe around my home. Also, the authors further state in their description of Coelocnemis that they are found "in conifer and oak-conifer woodlands throughout the state." There is indeed a large area of oak-conifer woodland near my home, but I have had frequent sightings of these beetles walking around in the neighboring arid, chaparral habitat where one might readily assume Eleodes species would be the norm.