The old-house borer, or house longhorn beetle (Hylotrupes bajulus) is a species of wood-boring beetle in the familyCerambycidae (longhorn beetles) and is the only Cerambycidae beetle that re-infests the same wood that it emerged from. Contrary to its name, it is more often found in new houses; this is in part because new home construction may use wood infected with the beetle's eggs if the wood is not properly kiln-dried in production but is mostly due to the beetles need for the higher resin content found in wood less than 10 years old. Originating in Europe, the old-house borer now has a worldwide distribution, including the Mediterranean, South Africa, Asia, USA and Canada. Recently it has been found in Perth, Australia. In Australia, it is known as the European House Borer.
Old-house borers prefer new softwoods, and particularly pine. Only the larvae feed on the wood. Larvae take up to thirty years to mature, depending on the moisture content of the wood and environmental conditions but typically mature in three to fifteen years, damaging the wood in the interim. Larvae usually mature in mid to late summer (July–August in the northern hemisphere), and the mature adults then cut large oval shaped exit holes 6–10 mm (¼ to 3/8 in) in diameter to exit the wood, leaving course powdery frass around the vicinity of the hole. Adults are most active in the summer. They are black or brown with grayish "hair" on their upper bodies and wing cases. They have shiny spots that resemble eyes.