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Wood Boring Insects

There are a number of insects, mainly beetles, which are able to use wood as a food source and some of them can cause serious damage to timber within buildings.  Wood boring insects all have fairly similar life cycles, although there are variations in the length of each stage in the life cycle, the type of wood attacked and the extent of damage caused.

The presence of damage caused by wood boring insects does not always indicate a need for remedial treatment and all of our Surveyors are trained to provide correct identification and provide any recommendations for treatment, if required.

Common Furniture Beetle (Anobium Punctatum)

Commonly known as Woodworm – generally the first signs to be seen of any wood boring insects are the small flight holes where the adult beetle has emerged.  However, the life cycle of this starts between one to three years prior to this, when the adult lays her eggs in a crack in the wood.

The emergence holes of this beetle are approximately 2mm in diameter but for every hole there is a tunnel beneath where the grub has eaten its way to the surface.  Therefore, although there appears to be little damage to the surface of the timber, the many tunnels may mean that replacement of timbers is necessary.

As the grub nears the edge of the timber it transforms into a beetle.  This adult beetle is capable of flying and, after it has mated, it may lay eggs in any convenient piece of wood and thus the whole cycle begins again.

Death Watch Beetle (Xestobium Rufovillosum)

In common with Woodworm, the first signs seen of this beetle are the holes in the surface of the timber.  The holes are 3mm in diameter and, therefore, much larger than those of the Common Furniture Beetle (woodworm).  Again, for every hole there is a tunnel and as this is a much larger grub, the damage to the timber can be excessive.

This beetle prefers hardwoods and can last within the timber for up to twelve years before metamorphosis takes place and the beetle emerges.  The characteristic tapping sound which we hear, is the male beetle knocking its head against the wood to attract a mate.

Heavily infested timbers, although looking solid on the exterior, can be completely eaten away inside and can become structurally unsound.  It may, therefore be necessary to carry out replacements of heavily infested timbers.  In some instances involving larger section timbers, resin repair works maybe required.

Death Watch Beetle bores deep into the timber and is notoriously difficult to completely eradicate in one treatment.

Wood Boring Weevil (Pentarthrum Huttoni)

This beetle is very distinctive with its long snout; it attacks wood that has rotted either through dampness or poor ventilation.  It consumes the soft portions of the timber before progressing on to the harder portions.

In contrast to other wood boring beetles, both the adult and the grub bore, producing tunnels running in the wood grain direction and leaving paper-thin walls between them.  Their life-cycle is very short, being less than one year.

The emergence holes are very small, 2mm in diameter, oval and have slightly ragged edges.

This beetle can also attack plywood due to the fact that it is bonded with animal and vegetable based adhesives.

Bark Borer (Ernobius Mollis)

Also known as the Waney Edge Borer, this insect is often mistaken by the layman for Common Furniture Beetle.

However, this beetle is not a true wood-borer, it confines its activities to the bark and immediate sapwood and dies out as soon as there is insufficient nutrients left in the bark and cambium on which to survive.

House Longhorn (Hylotrupes Bajulus)

This large wood boring beetle has oval emergence holes measuring up to 10mm long and 6mm wide.  The grubs bore along the grain of the wood, often near the surface and they can completely destroy the inside of joists and other timbers, leaving only a thin shell, without there being any visible sign of decay.  A slight corrugating of the surface veneer is often present when the damage is severe.

The females lay their eggs in cracks and crevices in the wood and these eggs hatch out in about two weeks.  The larvae crawl along the surface of the wood and then start boring into the timber.  They then stay in the timber for some three to eleven years eating their own length in one day.  As they are about 25mm long during the last stages, the damage caused can be substantial.

Lyctus Beetle (Lyctus Brunneus)

Also known as the Powder Post Beetle, this beetle lives off the sapwood of hardwoods.  It is a long, slim beetle which tunnels just below the surface, leaving a thin veneer of sound wood on the surface.  The emergence holes are 1-2mm in diameter.

Because this beetle needs starch in order to survive, it only lives in the sapwood or certain hardwoods. As plywood has a hardwood core it is susceptible but timbers over ten years old become immune as the starch depletes with age and this beetle is never found in softwoods.

It has a very short life-cycle of one year or less, which means the population increases very rapidly.

Forest Longhorn Beetle (Cerabycidae)

This large wood boring beetle has oval emergence holes, similar to those of the House Longhorn Beetle, and is common in large section hardwoods, principally oak.  It attacks standing or felled trees or partly dried timber where the bark is attached.  The damaged timber may sometimes be incorporated into buildings, and is commonly found in older roof structures.   Remedial treatment however, is not normally required.

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