The California mating-plug scorpions: stocky burrowers of the far-western hills, mild in venom and notable for the anatomical quirk the name records.
They dig committed burrows in firm ground and hold them for years, wanting deep, compacted substrate, arid conditions with a humid depth, and patience with an animal whose visible life is an entrance. Long lived, sedentary, low risk.
Western collection is thin and local, listings are occasional singles, and the genus trades to the completist's shelf of North American natives alongside its montane and dune neighbours. The burrow is the display, the mildness is the appeal, and the market is exactly as small as that combination suggests.