Ptilinus pectinicornis (Linnaeus, 1758)

Widely distributed across southern England and the midlands to south Yorkshire but lacking records from Cornwall, East Anglia and most of Wales. Although local it can be very common indeed where found. A wood borer, colonies of which are usually found in dry exposed Fagus wood but a wide variety of hosts have been recorded including Sambucus, Fraxinus, Acer, Quercus, Ulnus etc as well as plywood and ornamental timber ╣. Both standing and felled timber are attacked. Several large infestations have been found around Watford, two in Whippendell wood and one, the largest and with a huge population, in Cassiobury park. In each case in standing dead Fagus. The Cassiobury park colony has been active for at least four years and is quite fascinating to watch; during warm days in June both sexes are numerous and active upon the trunk from a metre or so above ground to the top, about 4 metres high. Males crawl quite quickly, constantly waving their antennae and, eventually, after ignoring many females will mate. Females are much less active and typically sit alone presumably signalling for a mate. During this intense activity more individuals are seen emerging from among the hundreds of pre-existing holes in the wood. Females, and less often so males, frequently disappear into these tiny holes. Tillus elongatus Lin. are numerous and very active among these swarms, their emergence holes are much larger and ignored by Ptilinus. All the while, for as long as the sunshine is warming the wood, there is a large swarm of Ptilinus of both sexes flying from about three metres around the top of the trunk. Although in fewer numbers and much less active the beetles can be seen patrolling the trunk all through the night. During 2006 this swarm was active during May, June and July. In 2007 May was uncharacteristically wet and the adults did not appear in numbers until mid June and then for about three weeks. Generally from late april until about mid July. Occasionally single specimens are seen on trunks or netted from most parkland around Watford, during 2006 several males were attracted to light in the town centre.
3.5-5.5mm. Distinctive due to the highly developed antennae; very strongly pectinate in the male and very broadly serrate in the female. Head deflexed, eyes much larger in male. Pronotum highly arched, tuberculate anteriorly and with strong granulate microsculpture although the female has smooth areas centrally and laterally behind middle. It is stated that the female, having excavated a brood chamber in wood and laid eggs, remains in the chamber with her pronotum plugging the entrance tunnel to protect the brood ╣. Elytra with indistinct rows of larger punctures among strong granular microsculpture. Head and pronotum black or dark brown, elytra lighter, entire upper surface with short dense golden pubescence. Legs red with femora, especially front pair, often darker. Tarsi 5-5-5 in both sexes.

Description from 4 Watford specimens at X40

╣Hickin, 1995. The insect factor in wood decay. Rentokil Library.