Pleocoma is the only extant genus of rain beetles (family Pleocomidae) and is endemic to the Pacific states of North America.

[1] Fossil remains of Pleocoma have been found in the Yixian Formation in China, suggesting beetles in this genus have existed in something like their present form since at least the Cretaceous period.

[3][4][5][6] Possessing a robust oval body form similar to other scarabaeiforms, their ventral side is densely covered with fine, long hairs (genus name derives from Greek πλείων (ple-, abundant) and κόμη (kome, hair), extending to the legs and to the margins of thorax and elytra.

[1] Larvae have the typical scarabaeiform characteristics, C-shaped bodies generally a creamy white.

The "triggering" conditions required for some species to fly are so stringent that a given population may only be active for a single day in a given year.