pellets in the frass. Adult beetles, alive or dead, may be present on the glass or the sills of windows, as may the specific enemies of the beetles in the same locations—a likely indication of specific wood-boring insects inside. Direct examination of the interior of the timber by destructive means is often not acceptable, and non-invasive means are required. Other means of identifying the wood-boring insects include pheromone traps; these are effective for the common furniture beetle and the house longhorn beetle (Hylotrupes bajulus) but not for the deathwatch beetle. However, adults of the deathwatch beetle are attracted to light. The sounds of the feeding larvae can be heard either unaided or with the help of a stethoscope, and X-ray scans and computer tomography can also be used. Similarly, active larvae may be identified by vibrations in the ultrasound range. The exit holes of deathwatch beetles are 2 to 3 mm (about 0.1 inch) in diameter, larger than those produced by the common furniture beetle. Deathwatch beetles will only attack buildings primarily made out of hardwood. Coniferous wood in buildings will be attacked only if it is in contact with the hardwood. Treatment This beetle was first described in 1668 by John Wilkins, but it was not until 1913 that the first scientific study was conducted by Professor Lefroy in an attempt to come up with a management solution for these beetles. The larvae of deathwatch beetle feed deep within timbers. Recent studies have suggested that most of the previously accepted practices of external application of insecticides are largely ineffective. Only gas fumigation remains effective, but poses considerable practical challenges in effectively sealing the larger, historic types of properties that these beetles are mostly attracted to. External insecticide application may, in fact, do more harm than good by killing the natural enemies of the beetle. One way of dealing with the problem may be with the use of ultra-violet "insectocutors", to attract and kill the adults that emerge from the wood in the spring. If there is concern about the strength of structural timbers, a structural surveyor can drill core samples to determine the condition of the wood. Modern techniques of ultrasound examination now allow the extent and localisation of an attack within timbers to be determined with great accuracy, and, for historic properties where damage to ornate plasterwork must be avoided, can be followed by micro-drilling and highly-targeted injection