Several species of small chalcids lay their eggs in the larvae of wood-boring beetles. They may directly hunt the larvae in their tunnels and one can often see these nimble little insects flying in and out of the holes in the timber, but some can lay their eggs through the timber with the help of their ovipositor. The chalcid larva lives as a parasite on the beetle larva and eventually kills it. There are records of up to 95 per cent of the beetle larvae in roof timbers being attacked in this way. When the adult chalcids emerge they often find their way out through the old exit-holes of beetle larvae or they may make their own very small exit-holes. The adult chalcids are attracted by the light and can sometimes be found in large numbers on windows