Who would have thought that there are insects out there living in family groups, communicating through their own language of clicks and squeals; where the male, female, and grown offspring work together to care for larval broods?

They are rare, but there are a few species out there like this–and the bess beetles are one of them.


Known by many names, these insects have been called “betsy beetles”, “patent leather beetles”, “bessbugs”, “bess beetles”, and “horned passalus beetles”. They belong to the family Passalidae, which contains around 500 species!

The bess beetles in our exhibit are Odontotaenius disjunctus.


Bess beetles are saproxylic, meaning they feed off of dead wood. Because of this, they spend their entire lives within rotting logs, which they use for food, shelter, and a place to raise young.

Bess beetles can be found in Mexico as well as southeastern North America, since these locations are known for their warmer, more humid climates.

Bess beetles gnaw tunnels through their dwelling places using powerful mandibles made for chewing. They line these tunnels with wood particles that keep in moisture and provide soft places for young to mature/feed from.

Bess beetles preferably inhabit deciduous logs. Oak is a favorite.

This log has been host to bess beetles for about two years. Note the holes peppering the log, as well as the fibers spilling out from within. It is incredible how swiftly these insects can consume a chunk of wood–since first becoming a home for the beetles, this log has degenerated and is now falling to pieces.

To attract bess beetles, simply place a log (oak is best) grain-up in a moist area during winter. Allow the log to sit and rot through the warm months. It may take up to a year or more for beetles to arrive.

To tell when your log has become a home to bess beetles, lift it up and observe the soil beneath the bottom of the log. If there are shallow paths, signs of wood pulp, and/or holes in the bottom of the log, it is a sign of a healthy bess beetle population.

Note the moist, tilled appearance of the soil that sits beneath the log. Sure enough, there are the bess beetles, slightly startled by the sunlight flooding their home.


As stated above, moist, rotting wood is required for bess beetles to survive. Adults will first ingest pieces of raw wood. Microscopic organisms will then feed off of the waste, which is little more than partially-digested wood pulp, and this mash will then be eaten again by the beetles. The microorganisms that feed off the pulp play a key role in assisting the beetles’ digestion.

Larvae will also be fed this partially-digested pulp. Adults take special care to feed their young, since the grubs cannot eat the log on their own.


After reaching full maturity, a bess beetle will seek out a mate and find a suitable log to settle down in. Together, the male and the female bore holes through the log, eating the wood and creating a home for their future broods.

Bess beetles communicate with one another using a language of clicks and squeals. There are fourteen different sounds that the beetles create–that’s quite a diverse vocabulary for an insect.

Bess beetles take a year to mature from egg to adult. Larvae that have emerged from the pupal case as adults will stay behind to help care for their younger siblings before exiting the log in search of a mate.

BESS BEETLE STRIDULATION: Listen closely for the squeaking/creaking sound. This is one of the 14 sounds in a bess beetle’s vocabulary.

Life Cycle

Bess beetles have a complex journey of growth.

Eggs are opaque and may appear slightly green. They are laid in soft chambers of the log and are tended to diligently by both the male and the female.

Larvae go through many different phases of growth and will shed their skin (molt) many times before pupating. It takes a year for a grub to become an adult, and many more weeks for the exoskeleton of a newly emerged beetle to harden.

When it comes time for larvae to pupate, the adult beetles will construct a protective layer of wood pulp around their young. The young will later emerge from the pupal case red in color and with very soft exoskeletons.

After emerging as adults, the beetles will survive for around one more year, during which time they will raise multiple clutches.

Keeping Bess Beetles

Bess beetles are very easy to keep in captivity and can make excellent classroom pets! Simply keep them in a secure plastic container with plenty of soft, damp wood chunks to eat. It is recommended that you give the beetles a chunk of wood that is large enough for them to create tunnels in.

Keep the enclosure damp. The beetles will stay hydrated from the moisture in the wood. No need to feed them–just make sure they always have wood to chew on!

The bess beetles here at the Microzoo make their homes in our Hollow Woods exhibit–a massive ring of oak stumps working together to create a mini ecosystem. There are at least four different bess beetle colonies inhabiting the Hollow Woods, living side by side and working together to break down the dead logs. They are on their second generation and counting!

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Research source: https://en.wikipedia.org/wiki/Passalidae