Bess beetles (family Passalidae) are large insects known for their shiny black exoskeleton. They are commonly found in forests across temperate and tropical regions, often under the bark of fallen trees. Bess beetles are recognized for their distinctive social structures and their role as nature’s decomposers. Understanding their nutritional needs provides insight into how they thrive in environments where few other large insects can find sustenance.
Identifying the Bess Beetle
The common North American bess beetle, Odontotaenius disjunctus, is easily recognized by its robust, one-to-one-and-a-half-inch-long body. Their shiny, black armor resembles polished material, leading to the popular name, Patent Leather Beetle. They are also sometimes called the Horned Passalus because a small horn projects from the head.
The body features two distinct sections: a smooth, rectangular middle segment (pronotum) and grooved wing covers (elytra). These beetles possess powerful mandibles adapted for chewing through dense material. Bess beetles live exclusively within decaying logs in hardwood forests, such as oak, hickory, or maple. Their antennae are distinctive, with the final segments splitting into comb-like projections that help them detect chemical signals within the wood.
The Primary Wild Diet (Wood Decomposition)
In their natural habitat, bess beetles are classified as saproxylophagous, meaning they specialize in consuming decaying wood. Wood is nutritionally poor, consisting mainly of complex polymers like cellulose and lignin. The beetles specifically target wood that has been softening and decomposing for roughly two years, often found just beneath the bark layer.
This decomposed wood has been pre-processed by fungi and microorganisms, which break down the tough plant cell walls. The beetles ingest this softened wood, but their digestive systems rely on a microbial community within their gut. To maintain this necessary internal flora, both adults and larvae engage in coprophagy, the practice of consuming their own feces, known as frass.
Adult beetles play an active role in feeding their young, which is unusual among beetles. The adults chew the wood into a fine, digestible pulp and feed this material, mixed with microbe-rich frass, directly to the larvae. This parental care ensures the larvae receive the necessary microorganisms to extract nutrients from the wood. The family group lives together within galleries excavated inside the dead log, which serves as both their shelter and food source.
Diet in Captivity and Supplemental Foods
Replicating the bess beetle’s natural diet in a captive setting requires providing the correct type of decayed wood. The foundation of their enclosure is a substrate made from soft, rotting hardwood (oak, maple, or hickory) that is moist enough to crumble easily. This wood should never be treated with chemicals, paints, or preservatives, as these substances are toxic to the beetles. The substrate is often supplemented with moist soil and decomposing leaves to mimic the forest floor environment.
The main goal is to provide a consistently moist supply of decaying wood, which the beetles will tunnel through and consume. When maintaining a colony, do not clean the enclosure completely, as the frass containing symbiotic microorganisms must remain for the beetles to re-ingest. Adding fresh pieces of suitable rotting wood periodically ensures the colony has a continuous food supply.
While decaying wood is the only requirement for long-term health, owners can offer supplemental foods occasionally for variety and extra moisture. Small pieces of fruit (such as apple slices or banana) and vegetables (like carrots or cucumbers) are accepted by some beetles. These items should be offered infrequently and removed quickly if uneaten (within 24 to 48 hours) to prevent the growth of mold or mites.