Hadrobregmus pertinax

Hadrobregmus pertinax is a species of woodboring beetle within the genus Hadrobregmus of the family Anobiidae. The adult is black, with yellow hairs at the back corners of its head, and is 4-5 mm long. The larva is white, about 5 mm long, and lives in decaying wood. The larval stage lasts many years. The Finnish name is "kuolemankello," literally the "clock of death," which comes from the sound resembling the ticking of a clock, made by the male striking its head against the surface of the wood in order to attract a mate. It is the most destructive insect of buildings in Finland, where it survives the long winters in below-freezing temperatures. Because the larva lives in decaying wood, its presence indicates moisture damage. Resolution of the moisture problem will cause the beetle to leave.