Pleocomidae

Definition

A family of beetles (order Coleoptera, superfamily Scarabaeoidea) containing the rain beetles, currently treated as the sister group to all other families of Scarabaeoidea. The family comprises one extant genus, Pleocoma, restricted to western North America, plus two extinct genera (Cretocoma and Proteroscarabeus) known from Late Cretaceous deposits in Asia. Adults emerge primarily in response to rainfall or snowmelt, giving rise to the common name.

Etymology

From the type genus Pleocoma (Greek pleos 'full' + kome 'hair', referring to the densely setose body) + -idae family suffix.

Example

Pleocoma hirticollis, a rain beetle in the family Pleocomidae, emerges from burrows in California oak woodlands following winter rains to mate and disperse.

Related Terms

• Scarabaeoidea
• Scarabaeidae
• Pleocoma
• sister group
• Cretaceous
• fossil beetle
• rain beetle

Usage Notes

Formerly classified within Scarabaeidae; current taxonomy recognizes Pleocomidae as a distinct family based on morphological and molecular evidence. The family's relictual distribution and basal phylogenetic position make it significant for understanding scarabaeoid evolution. Specialists may encounter the family under older classifications in historical literature.