Passalidae

Definition

A family of scarabaeoid beetles (order Coleoptera) commonly called bess beetles, bessbugs, or horned passalus beetles, comprising approximately 500 species, nearly all tropical, with North American species notable for large size (20–43 mm), a single cephalic horn, and subsocial behavior including parental care and communication via stridulation—unusual traits among beetles.

Etymology

From the genus Passalus + -idae (family suffix)

Example

Passalidae larvae feed on decaying wood pre-chewed by adults, and adults and larvae communicate through audible stridulation produced by rubbing the middle and hind legs against a file on the elytral undersurface.

Synonyms

• bess beetles
• bessbugs
• horned passalus beetles
• betsy beetles
• betsy bugs

Related Terms

• Coleoptera
• Scarabaeoidea
• subsocial behavior
• stridulation
• xylophagy
• cephalic horn
• parental care
• decay succession

Usage Notes

The common name 'bess beetle' (or variants like 'bessbug,' 'betsy beetle') is widely used in North American literature but refers specifically to the genus Odontotaenius and relatives; tropical Passalidae lack the common name and often lack the prominent horn. The family is sometimes placed in its own superfamily Passaloidae or within Scarabaeoidea depending on phylogenetic interpretation. Social behavior in Passalidae represents one of the few documented cases of subsociality in beetles, involving extended family groups in rotting logs.