The Passalid beetle, Odontotaenius disjunctus, or Bess Beetle lives in communities in rotting logs. The adults build tunnels as they feed. Rotting wood is a poor source of many nutrients that insects need for development. Adult Passalid Beetles host a garden of symbiont microorganisms in their hindgut. The microorganisms benefit from processing and ingestion of the wood by the adult beetles. The symbionts contribute important nutrients to the Passalid Beetles.
Passalid Beetle larvae grow very slowly. The larvae are dependent on the adults for food and cannot survive in the absence of care by their parents. The larvae feed on food that has been passed through the intestine of the adults and allowed to incubate. The incubation is believed to allow microorganisms to further process the excrement into a food that is nutritious enough for the larva.
Mining a log and building up a store of microbe enhanced food requires time and effort by the adults. It is not surprising that adults are territorial and will evict conspecific intruders by pushing, shoving and flipping intruders onto their backs. In some instances, intruders that take over a nest will kill the larvae of the Bess Beetles to eliminate competition from their own offspring.
Passalid Beetles adapt well to living in laboratory colonies. Their sub social lifestyle and sophisticated repertoire of behaviors make them interesting subjects for scientific studies.