House longhorn beetle

Habitat:

Found in the sapwood of most softwoods, particularly roofing timbers. At present only common in the area of England SW of London (mainly Surrey) where special Building Regulations exist to protect structural timber and prevent further spread. There are small inactive infestations in buildings over 100 years old in London. In other parts of the country isolated infestations usually stem from imported infested packing cases. It is very occasionally found in softwood plywood.

Damage characteristics:

May be overlooked in the early stages. With large infestations, larval feeding can be heard as a scraping noise on warm days.

Emergence holes are few, large, often ragged, ovals, 6-10 mm diameter.

Tunnels are oval, 6-10 mm diameter. They are extensive and join up to cause almost complete disintegration of sapwood, but leaving intact a thin surface skin. Dust-filled tunnels may cause blisters or corrugations on the the surface of the wood which can be highlighted with oblique torch light.

Bore dust is cream-coloured, sausage-shaped pellets, gritty when rubbed between the fingers. Small chips and wood fibres may be present.

Note: details of suspected outbreaks should be reported to the Building Research Establishment's Timber and Protection Division, which maintains records of infestations in the UK.

Insect characteristics and location:

Adults 10-20 mm long, black or dull brown. Smoth central line on thorax flanked by two shiny black bumps. Two grey patches of hairs on wing covers.

Larva up to 30 mm long, straight, pale cream. Three pairs of very small legs, three small black dots on either side of mouth. Found all year round in infested timber.

Damage - emergence holes

Photographs of adult from above
and in front