10 Fascinating Facts about Bess Beetles

Interesting Traits and Behaviors of Passalids

Bess beetles.
Bess beetles are fascinating insects. Getty Images/PhotoLibrary/John Macgregor

The amiable bess beetles (family Passalidae) make great classroom pets, and are fun to watch. Bess beetles are so much more than cute; they're also some of the most sophisticated bugs on the planet. Don't believe it? Consider these 10 fascinating facts about bess beetles.

1. Bess beetles are important decomposers

Passalids live in hardwood logs, munching away on the tough tree fibers and turning them into new soil. They prefer oak, hickory, and maple, but will set up shop in just about any hardwood log that has sufficiently decayed. If you're looking for bess beetles, turn over rotting logs on the forest floor. In the tropics, where bess beetles are more diverse, a single log may house as many as 10 different Passalid species.

2. Bess beetles live in family groups

Within their log homes, both bess beetle parents reside with their offspring. With their powerful mandibles, they excavate rooms and passages to house their family. The bess beetle family guards its home against any and all intruders, including other unrelated bess beetles. In some species, a large, extended family of individuals lives together in a colony. This subsocial behavior is quite unusual among beetles.

3. Bess beetles talk

Like many other insects – crickets, grasshoppers, and cicadas, for example – bess beetles use sounds to communicate with one another. What's remarkable, however, is how sophisticated their language seems to be. One North American species, Odontotaenius disjunctis, produces 14 distinct sounds, presumably with different meanings. An adult bess beetle "talks" by rubbing a hardened part of its hindwings against spines on the dorsal surface of its abdomen, a behavior known as stridulation. Larvae can communicate, too, by rubbing their middle and hind legs against each other. Captive bess beetles will complain loudly when disturbed in any way, and squeak audibly when handled.

4. Bess beetles co-parent their young

The vast majority of insect parents simply deposit their eggs and go. A few, like some stink bug mothers, will guard her eggs until they hatch. In fewer still, a parent might stick around long enough to keep her nymphs safe. But rare are the insect parents that remain together as a pair to raise their young to adulthood, and bess beetles are counted among them. Not only do the mother and father bess beetle work together to feed and protect their offspring, but the older larvae stick around to help with rearing their younger siblings.

5. Bess beetles eat poop

Like termites and other insects that feed on wood, bess beetles need the help of microorganisms to break down the tough plant fibers. Without these digestive symbionts, they simply couldn't process the cellulose. But bess beetles aren't born with these vital fungi and bacteria living in their guts. The solution? They eat their own poop, much like rabbits do, to keep a healthy number of microorganisms in their digestive tracts. Without enough frass in its diet, a bess beetle will die.

6. Bess beetles lay their eggs in nests of poop

Baby bess beetles are at an even greater digestive disadvantage, because their mandibles aren't strong enough to chew wood and they lack gut microorganisms. So mama and papa bess beetle start their babies out in a cradle made of masticated wood and frass. In fact, when a bess beetle larva reaches its final instar and is ready to pupate, its parents and siblings work together to construct it a cocoon made of frass. That's how important poop is to a Passalid.

7. Bess beetles have a lot of nicknames

Members of the family Passalidae go by a long list of common names: bessbugs, bessiebugs, betsy beetles, bess beetles, horned passalus beetles, patent leather beetles, peg beetles, and horn beetles.  The many variations on bess seems to derive from the French word baiser, which means "to kiss," and is likely a reference to the smooching sound they make when they stridulate. If you've seen one, you already know why some people call them patent leather beetles – they're quite shiny and black, like patent leather shoes.

8. Bess beetles look menacing, but are surprisingly gentle

The first time you see a bess beetle, you might be a bit intimidated. They're hefty insects, often well over 3 cm long, with the massive mandibles you'd expect from a beetle that eats wood. But rest assured, they don't bite, and don't even grab hold of your fingers with their feet the way scarab beetles do. Because they're so easygoing and big, they make good first pets for young insect lovers. If you're a teacher interested in keeping insects in your classroom, you won't find one easier to care for and handle than the bess beetle.

9. Most bess beetles live in the tropics

The family Passalidae includes roughly 600 described species, and nearly all of them live in tropical habitats. Only four species are known from the U.S. and Canada, and of these, two species haven't been seen for decades. Some bess beetle species are endemic, meaning they live only in a certain area, such as on an isolated mountain or a particular island.

10. To date, just a single bess beetle fossil has been found

The only prehistoric Passalid known from the fossil record is Passalus indormitus, collected in Oregon. Passalus indormitus dates to the Oligocene epoch, and lived about 25 million years ago. There are no known bess beetles living in the Pacific Northwest today, interestingly. Passalus indormitus is most similar to Passalus punctiger, a living species that inhabits Mexico, Central America, and parts of South America.


  • Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, by Douglas W. Tallamy
  • American Beetles: Polyphaga: Scarabaeoidea through Curculionoidea, Volume 2, edited by Ross H. Arnett, JR, Michael C. Thomas, Paul E. Skelley, J. Howard Frank
  • Insect Behavior, by Robert W. Matthews, Janice R. Matthews
  • Ninety-nine Gnats, Nits, and Nibblers, by May Berenbaum
  • Bess Beetles of Kentucky, University of Kentucky Entomology website. Accessed December 10, 2013.
  • Borror and DeLong's Introduction to the Study of Insects, 7th edition, by Charles A. Triplehorn and Norman F. Johnson
  • Encyclopedia of Entomology, 2nd edition, edited by John L. Capinera.
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Hadley, Debbie. "10 Fascinating Facts about Bess Beetles." ThoughtCo, Apr. 5, 2023, thoughtco.com/fascinating-facts-about-bess-beetles-1968123. Hadley, Debbie. (2023, April 5). 10 Fascinating Facts about Bess Beetles. Retrieved from https://www.thoughtco.com/fascinating-facts-about-bess-beetles-1968123 Hadley, Debbie. "10 Fascinating Facts about Bess Beetles." ThoughtCo. https://www.thoughtco.com/fascinating-facts-about-bess-beetles-1968123 (accessed June 10, 2023).