Wood boring insects refer to a selection of arthropods which cause damage to wooden structures. This group of insects feature a range of species of insect at different stages of their life cycles from larvae to adults.

Wood boring insects are seen as pests due to the damage they create in both urban, and rural areas. Within an urban environment wood boring insect can cause a huge amount of damage to residential properties. Whilst in agricultural and rural settings, wood boring insects are responsible for damaging crops. However, it’s worth noting that some wood boring insects are a key part to the ecosystem, helping to recycle dead trees. There are some cases though where wood boring insects have become an epidemic in some forests killing a large number of trees.

Woodworm is a generic term used for a number of species of wood-boring beetle and refers to the larvae of the beetles, which feed on wood after hatching from the egg, creating tunnels in the process. They only emerge from the timber after pupating and developing into adults, creating the

characteristic holes in the wood surface.

This characteristic also leads to the misconception that the holes can be treated with insecticide to kill the beetle, when in fact it is pointless as the hole signifies that the beetle has left.

The main beetles that cause damage to structural timber and wooden fittings, furniture and items in buildings are classified into three groups, commonly called: deathwatch (Anobiidae family), powderpost and false powderpost beetles (Bostrichidae family).

Beetles are the largest group of insects, having about 400,000 species in 500 families. They are extremely diverse with species adapted for almost any kind of environment and to feed on any food source, including many agricultural, horticultural and forestry plants and products. Many species are also beneficial predators of other insect pests.

Beetles have the basic insect anatomy of head, thorax and abdomen, but are characterised by a hard exoskeleton, hard forewings and abdomen with numerous hard plates. They also have the typical insect lifecycle of egg, larva with several stages of growth (instars), pupa and adult.

Several species of beetle in the Anobiidae family are called death-watchbeetle. The species well known in Europe, and the source of the name, is Xestobium rufovillosum.

The beetles get their name because of their habit of tapping on wood, usually at night, to attract a mate.

Deathwatch beetles mainly infest moist and partly decayed softwood timber that has moisture content over 14%. They are more likely to be found in damp buildings or areas of buildings with poor drainage or water leaks. They are unlikely to be present in buildings with central heating where the moisture content is low.

The beetle larvae fill their tunnels with frass that has a slightly gritty texture, but less coarse than false powder-post beetles. The exit holes can be of varying sizes but are larger than powder-post beetle holes.

The furniture beetle only infests dry, seasoned sapwood of hardwood and conifer trees. It causes more damage in structural timbers and joinery than in furniture. The females lay their eggs in cracks in the surface of wood or inside old exit holes. The eggs hatch into larvae in a few weeks and bore into the wood.

larvae mature over 3-4 years, eating their way through the timber. After pupating near the surface of the wood and adults make an exit hole 1-1.5mm in diameter. An active infection is shown by the presence of

wood dust around holes. As the larval stage lasts several years there can be an active infestation with no visible signs during this period. The actual time of development to the adult depends on type of wood, temperature and humidity.

Attacks sapwood of hardwood and softwoods, plywood and wattling.

Tunnelling in sapwood tends to run along the grain. Tunnels relatively short and contain a loose bore dust. Bore dust feels ‘gritty’ and under magnification it is uniform in colour and contains ‘lemon’ shaped pellets. The damage can be confused with Ambrosia beetle, Waney Edge Borer and Weevil.

This beetle will also attack softwoods, but only those with some kind of bark present. These borers are not necessarily a major threat. They will leave holes around 2 mm in diameter and pellets that are bun-shaped. While often confused with the furniture beetle, they inflict no real damage.

Seasoned and partly seasoned timber with bark present. Bark presence required to initiate attack. Surface scoring to outer sapwood, some holes present. Most damage present in bark.

Gritty, round shaped pellets of uniform colour. Round tunnels mainly in the bark if present. Round flight holes of approx. 2mm diameter.

Weevil subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae), which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead or stressed trees in which they cultivate fungal gardens, their sole source of nutrition. After landing on a suitable tree, an ambrosia beetle excavates a tunnel in which it releases spores of its fungal symbiont. The fungus penetrates the plants xylem tissue, extracts nutrients from it, and concentrates the nutrients on and near the surface of the beetle gallery. Ambrosia fungi are typically poor wood degraders, and instead utilize less demanding nutrients.

The majority of ambrosia beetles colonise xylem (sapwood and/or heartwood) of recently dead trees, but some attack stressed trees that are still alive, and a few species attack healthy trees. Species differ in their preference for different parts of trees, different stages of deterioration, and in the shape of their tunnels ("galleries"). However, the majority of ambrosia beetles are not specialised to any taxonomic group of hosts, unlike most phytophagous organisms including the closely related bark beetles.

One species of ambrosia beetle, Austroplatypus incompertus exhibits eusociality, one of the few organisms outside of Hymenoptera and Isoptera to do so.

Ambrosia beetles have been placed in independent families Scolytidae and Platypodidae, however, they are in fact some of the most highly derived weevils. There are about 3,000 known beetle species employing the ambrosia strategy.

Beetles and their larvae graze on mycelium exposed on the gallery walls and on bodies called sporodochia, clusters of the fungus' spores. Most ambrosia beetle species don't ingest the wood tissue; instead, the sawdust resulting from the excavation is pushed out of the gallery. Following the larval and pupal stage, adult ambrosia beetles collect masses of fungal spores into their mycangia and leave the gallery to find their own tree.

The damage occurs in the forest, the insects attacking standing trees and freshly felled logs’ tunnelling into the wood for long distances across the grain. No bore dusts. Unlike most woodborers the adult does the tunnelling.

Surfaces of tunnels are coloured black/blue-black. Holes vary in size depending on which of the ambrosia beetles caused the damage, many about the same size as furniture beetle holes.

The damage is usually confused with Common Furniture Beetle damage, but it occurs in the log. These insects cannot infest seasoned timber.

hardwoods and some softwoods. Tropical timber and bamboo transported in international trade are

often infested with the beetles. The common products infested with the beetles include flooring, panelling, furniture and other hardwood items.

The females do not lay their eggs on the surface of the wood, but a ‘gallery’ into wood to lay their eggs in pores or cracks. The larvae of this group pack their tunnels with a course, gritty frass, which distinguishes

them from other types of wood borer.

this beetle has been reclassified into a new subfamily of the Bostrichidae beetle family, called Lyctinae. It was previously in a separate family, Lyctinae, so some descriptions still refer to this old classification. There are eleven species of the genus Lyctus recorded in the Global Biodiversity information facility.

Lyctus brunneus, is the most common species found throughout Europe and has also been recorded in South Africa, Australia and Japan.

Powderpost beetles tend to attack the sapwood of certain hardwoods and bamboo that have large pores in the wood in which they can lay their eggs and that have a high starch content, such as oak, ash, walnut, mahogany. Imported tropical hardwoods are often infested with the beetles.

Hardwoods with smaller pores such as birch and maple are rarely infested and softwood, which is from conifers and has lower nutrients, is never infected. The beetles also prefer dry wood, feeding on wood as low as 8% humidity.

The starch content reduces with the age of the timber, therefore powderpost beetles are rarely found in old timber. They are more common in new homes and recently manufactured hardwood items such as windows and door frames, panelling, flooring, plywood and furniture. Powderpost beetles are unlikely to infect structural timbers as these tend to be made from softwood. Wood that has a finish, such as paint, varnish or wax will not have a new infection, but the beetles can already be present when it is processed and can still emerge later.

These beetles are called powderpost because the larvae produce a characteristic fine, dust-like frass with the consistency of flour or talcum powder, as they feed on the wood and bore the tunnels. This distinguishes them from other types of woodworm.

The adult females lay their eggs on the surface of wood or in cracks. The life cycle ranges from three months to over one year, depending on temperature, humidity, and the nutritional quality of the wood.

is native to Europe but has been spread to many areas worldwide through the trade in timber and wood products. It is a pest of seasoned sapwood of softwood timber. It is more often found in new homes, infesting younger timber, rather than timber in old buildings. The life cycle takes up to 10 years, depending on environmental conditions and the nutrient content of the wood, which decreases with age.

Infestation in homes is caused mainly by using timber already containing the eggs or larvae. They feed on the wood, mainly near the surface, until maturing into the adults. The larvae are larger than many wood boring larvae, up to 2.5cm long and they cut larger exit holes 6-10mm in diameter.

The Asian longhorn beetle (Anoplophora glabripennis) and citrus longhorn beetle (Anoplophora chinensis) are native to East Asia but have been introduced to other areas of the world, most significantly Europe and North America. The Asian longhorn beetle is a pest of hardwood trees in roadside plantings and plantations in China and has now become a pest in Europe and the US. In the US it tends to attack Acer

species. The citrus longhorn beetle is a pest to over 100 species of tree and shrubs.

The adult female of the Asian longhorn beetle chews a small pit in the bark to lay each egg. The larvae feed within the vascular layers of the tree, the citrus longhorn in the lower part of the tree and the Asian longhorn in the upper trunk and branches. The adults make a round exit hole about 10mm in diameter.

The wharf borer, has been found in many temperate countries including the UK, Australia, New Zealand, France, Japan and all the US except Florida. The beetle is found where there is moist decaying wood, such as in docks, harbours, jetties and along rivers and coastal areas. The females lay eggs on the rotten timber and the eggs hatch in 5-11 days. The larvae burrow about 1cm below the surface, then tunnel into the wood to feed. The larval stage can last from two months to two years, depending on conditions. The adults do not feed, living only a few days to mate and find a new site to lay eggs.

The wharf borer is a ‘secondary pest’ as it feeds on already rotten timber, but its tunnels can further weaken the timbers.

Bark beetle are now regarded as a specialised section of the weevil family, in the subfamily Scolytinae, which has about 6,000 species in 2200 generas.

Bark beetles can be pests of tree crops – in forestry and agriculture – and logs in storage or transport. They introduce fungi that attack the wood, killing the tree or introducing decay in stored logs.

In natural forests, bark beetles are important in recycling weakened and dying trees and creating habitats for other insects and fungi. They also play a major role in making patches where new trees can regenerate, creating more diverse forest ecosystem.

Some species, however, break out into epidemics in forests with high densities of single species, killing trees over large areas.

The female lays eggs in the phloem layer, the moist inner layer of the bark next to the sapwood species mine a short chamber in the bark for depositing the eggs or also mating. The larvae feed on the phloem layer, leaving characteristic patterns of tunnels in the outer wood of the tree.

The Weevils are a large class of Beetles, having distinct snouts, from which spring the antennae or feelers. There are two species of Weevil which are found in structural timbers-Pentarthrum huttoni and Euophryum confine; they have no popular names. They are small, dark brown or black beetles, about 1/8 inch in length, and are easily distinguished by their pronounced snouts.

The two wood-boring weevils are recognized with increasing frequency in the London district and in other parts of the country, almost always in timber which is damp or infected with fungus-usually wet rot. It is not unusual to find hundreds of adult weevils crawling about on the surface of the rotten wood. Weevils will continue activity in infected wood after it has been dried out to halt the wet rot.

Weevils tend to consume the soft portions of the timber (spring-wood) before the harder portions, giving attacked wood a peculiar appearance. In contrast to other wood-boring beetles, both the adult Weevil and the grub bore. Exit holes are very small, often oval with ragged edges.

The life-cycle is less than one year.

Pentarthrum is sometimes found in beer barrels-which naturally are dampand then proceeds to burrow in the woodwork of public house cellars.

The larvae of some species of clearwing months of the family Xyloryctidae (Australia) and Sesiidae (Europe, North America, tropics, Australia) are important wood boring pests in ornamental and timber trees. There are over 1,300 species of Sesiidae, many resembling wasps and hornets, in both looks and behaviour. This enables them to be active in daylight, unlike most moths.

The females deposit the eggs in crevices or broken bark and after hatching the larvae burrow into the bark and sapwood of the tree. They mainly target trees that are already stressed or damaged, such as from drought or injury. Clear wing moths infest alder, ash, birch, fir, oak, pine, poplar, sycamore, willow and several types of fruit trees. Commercial products containing nematode worms that are parasites are available to control outbreaks.

There are around 500 species of the carpenter bee, nearly all building nests in dead wood or bamboo. They are often similar in size and appearance to bumble bees, but are distinguished by having a hairless, shiny upper abdomen.

Carpenter bees do not eat wood, the adult female bee excavates tunnels 3-6 inches long in the wood to lay the eggs. The eggs are laid in a set of small cells in branching tunnels or separated by a thin sliver of wood along a tunnel, each provided with a ball of pollen on which the larvae can feed. The entrance hole is perfectly round, about half an inch diameter – the size of a finger. The female can enlarge old tunnels or create new ones for egg laying. The bees are generally solitary but can ‘cohabit’ or nest in groups.

When a bee is active there may be coarse sawdust beneath the entry hole and scraping sounds heard coming from within the wood. Carpenter bees prefer bare or weathered wood, so painted or treated wood is a deterrent.

Carpenter ants are common in forest areas around the world, with 1,000 species in the genus camponotus. They do eat wood but build their main nest by tunnelling in damp wood where the moisture is high enough for the eggs to survive. They also establish satellite nests in drier wood that can contain workers, pupae and mature larvae.

Carpenter ants will readily invade buildings to forage for food and establish nests in wood that provides the right environment for colonies – such as wood that is kept moist by leaks, condensation or poor air circulaton. They also nest in any small spaces in a building with the right moisture conditions, such as behind bathroom tiles or round badly fitting window frames. The satellite nests, which require less moisture for the colony to survive, can be stablished in almost any void in a building.

The parent colony can also be outdoors while the satellite colonies are in a building, with the ants constantly travelling between the two. Carpenter ants can be large ants, 0.3-1 inch, but even within a colony there are different sized ants with different roles.

The ants feed on protein, often dead insects, and carbohydrates, especially the honeydew produced by aphids and scale insects.

There are several families of wasp whose larvae bore in wood or takeover existing tunnels in wood made by other insects. The main family that attacks trees is the Siricidae, or horntails, named because of a horn like feature on the abdomen of the larvae.

The female wood wasp has a needle-like ovipositor that it uses to drill into a suitable point in the wood of dead or dying trees to lay the eggs. It also squirts a fungus-containing liquid onto the wood that digests the wood for the larvae to feed on. The eggs hatch into larvae in three to four weeks and tunnel into the fungus-digested wood as they feed on it, usually parallel with the grain, resulting in a tunnel about 25-30cm long. The larvae mature in one to five years, depending on conditions, moving to just below the wood surface before pupating. The adult emerges by chewing an exit hole 6-12mm in diameter.

The wood wasp lays eggs in already damaged trees, but the introduced fungus can rapidly deteriorate the timber. It will not infest wood in homes but can be brought into homes in finished timber. The damage to buildings caused by wood wasp is mainly cosmetic, resulting from their exit holes in timber, but also through other substances covering the timber, including plaster, linoleum, carpets and other flooring materials.

One species of wood wasp, Sirex noctilio, is regarded as an invasive pest. It is native to Europe, Asia and north Africa, but has been introduced to the US, New Zealand, Uruguay, Argentina, Brazil, Chile and South Africa, probably through international trade involving timber.