Kudos to @ivanparr for choosing a great spot for these. We found them exclusively on the undersides of rather rotten hardwood logs and branches (mostly of Umbellularia californica), generally on shoulders above the creek where there was ample soil moisture. They were ~1.5 mm long (photo with the green ruler has mm as the minor lines), a bit more purple-toned than Megacina cockerelli, and considerably less active and prone to run away than that species. They would remain in that "leg cage" posture for many, many minutes before deciding to relocate. Juveniles seemed much more active than the adults.