Definitely a new species. Entirely subterannean in habits, seemingly very restricted in range and only found on forested mountains in Marin and Sonoma county. Probably fairly sensitive to development and habitat disturbance.
Over a dozen of these were found under various rotting Populus logs, usually clinging to drier parts of the wood in loose aggregations of adults and juveniles. Under one log they were living near a Latrodectus specimen.
They would tend to freeze at first, before slowly starting to go around in ever-widening circles in search of cover.
Outside temperature was in the low 50s°F.
Thanks,
Arthroverts