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Bess Beetles, Family Passalidae


Bess beetles live in rotting logs.

Bess beetles live in rotting logs. They're shiny black, with grooved elytra and a gap between the elytra and the pronotum.

Jessica Lawrence, Eurofins Agroscience Services, Bugwood.org

Bess beetles live together in family groups, with males and females sharing parenting duties. They go by quite a few common names: bessbugs, patent leather beetles, horn beetles, Betsy beetles, and peg beetles. Bess beetles belong to the family Passalidae and share certain habits and traits.


Bess beetles can be quite large, measuring up to 70 or 80 mm in length. They're shiny and black, which is why some people refer to them as patent leather beetles. You'll notice a pronounced gap between the deeply grooved elytra and the pronotum. A single groove divides the pronotum in two.

To distinguish bess beetles from other similar beetle families, you'll also need to examine the head, mouthparts, and antennae. The bess beetle's head will be narrower than the pronotum, and the mouthparts project forward. The antennae have 10 segments, and are not elbowed. They terminate in a 3-segmented club.


Kingdom – Animalia
Phylum – Arthropoda
Class – Insecta
Order – Coleoptera
Family - Passalidae


Both adults and larvae feed on decaying wood. Both male and female bess beetles prepare the food by chewing it before feeding it to their young. Adults and larvae also feed on adult feces, which is predigested by microorganisms that break down cellulose.

Life Cycle:

Bess beetles undergo complete metamorphosis. Adults mate within the tunnel system they excavate in a rotting log. The female lays her eggs in a nest made of masticated wood.

Bess beetle larvae prepare to pupate about two months after eclosure from the egg. With the help of adults, the larvae constructs a pupal case made from frass. The larva works from the inside, and the adults from the outside. Adult bess beetles may live for over two years.

Special Adaptations and Defenses:

Kids often like bess beetles because they squeak when you disturb them. Adult bess beetles stridulate by rubbing the undersides of their wings across their abdomens. Larvae can "talk," too. Bess beetles have a remarkably complex language, making 14 distinct sounds.

Range and Distribution:

Entomologists list over 500 species of bess beetles worldwide, most living in the tropics. Just two species inhabit the U.S..

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