Horned Passalus Beetle, Odontotaenius disjunctus (Illiger) (Passalidae)

By Jody Cox

Horned passalus, Odontotaenius disjunctus (Illiger). © 2012, A.V. Evans.

Horned passalus (a.k.a. betsy, bess, or patent leather beetles) (Odontotaenius disjunctus) (Illiger) (28.0 – 37.0mm) are shiny black and straight-sided with a short hooked horn on the head and distinctly grooved wing covers (elytra); they are sometime covered with mites. Their bluish, c-shaped larvae have small paddle-like hind legs that are used to make squeaking sounds to communicate with adults. The larvae take about a year to reach adulthood. Both adults and grubs live together in galleries chewed in decomposing logs and stumps and eat decayed wood. The larvae are dependent upon food that has been pre-chewed by the adults to obtain gut-organisms that help them to digest wood. The adults produce a squeaking sound by rubbing their elytra on the abdomen when communicating with the larvae or if alarmed.


Drees, B.M. and J. Jackman. 1999. Field Guide to Texas Insects. Gulf Publishing Company, Houston, TX.