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The patent-leather beetle or "Jerusalem beetle" (Odontotaenius disjunctus) is a beetle in the family Passalidae which can grow to just over an inch-and-a-half long. They are shiny black and have many long grooves on their elytra (outer wings). They have a small horn between their eyes, and clubbed antennae. When disturbed, adults produce a squeaking sound by rubbing their wings on the abdomen.This is called stridulating and is often easy to hear. This is apparently used for communication between members of the colony, possibly to communicate danger to other beetles.
Patent-leather beetles are usually found under, or inside, old logs or stumps. They eat old decaying wood. These beetles make tunnels in the wood, called "galleries." Inside the galleries, the beetles will mate, lay eggs, and raise their young. Larvae hatch from the eggs; they look like white grubs. The adults feed the larvae a chewed-up mixture of wood chips and feces. The larvae cannot feed themselves. Patent-leather beetle larvae take a year to develop. When the larvae are ready, they become pupae. Adults hatch from the pupa. Adult beetles are often covered by mites.
Many patent-leather beetles may live together in a colony in the same log. Adults can live over a year. Patent-leather beetles like to eat logs of certain trees. Mostly they eat deciduous trees (ones where the leaves fall off in the fall), such as oaks and elm. Wood infested by these beetles is usually well decomposed and falls apart readily.
The patent-leather beetle is considered beneficial in its activities to decompose dead wood, and is medically harmless.