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Adult male rain beetles are densely clothed with fine, erect and appressed pubescence ventrally, with a mixture of several different pubescence types over most of the appendages, long hairs and bristling setae on the head, a row of curved setae on the lateral margins of the elytra and thorax, and in some species, a pubescent pronotal disk. Females generally are less pubescent overall than males, but the patterns of hair distribution generally are the same.
The scarabaeoid beetle family Pleocomidae contains but a single extant genus, Pleocoma LeConte, 1856, encompassing 34 currently-recognized species collectively distributed in forest, chaparral and grassland habitats along the western coast of North America from southern Washington to northern Baja California, Mexico. Commonly called ?rain beetles,? male Pleocoma typically are active during the Winter season, and most often are encountered flying during or shortly after rainfall, or over melting snow. The much larger, brachypterous females emerge from the soil at the onset of rain, emit a sexual pheromone to attract males, and following mating, await the maturation of their eggs. A lengthy larval development period is spent underground, moving through the soil or situated within a hard-packed burrow, feeding upon organic matter in the soil.
