Cannot be tamed.
Located in Mysterious Cave, Zaralek Cavern. Can be found during the Sniffenseek dig, "Thieving Critters". Spawns when you use Myrrit to burrow and then 'dig' on the moving dust patch in the western tunnel branch. Note that taming this beetle (instead of killing it for the key) will temporarily delay completion of the dig, but it's possible for a new dust patch to spawn (leaving and re-entering the dig may help reset it).