The Common Furniture Beetle (Anobium punctatum) is a type of woodworm that belongs to the family Anobiidae. Despite its name, the term “common” with emphasis on ‘furniture’ is misleading, as this beetle primarily resides in the sapwood of structural and joinery timber. The larvae bore into the sapwood and then pupate into adult beetles. When the adult beetle exits the timber, it creates exit holes or flight holes. The life cycle then begins anew. This species of woodworm often infests the timber of UK homes.

Its Life Cycle

Mating: –

This often occurs within a few hours of emergence from its exit hole. Females sometimes stay in an old exit hole, both before and after mating. Mating can occur with the female just inside an old flight hole. Her abdomen tip protrudes, while the male is usually on the outside.

Eggs: –

The female lays her eggs in cracks of unpolished or unpainted wood. Sometimes she lays them in old exit holes.  The eggs are laid in groups, but not necessarily all in the same place. There may be 20-100 eggs. The eggs are oval but become distorted when forced into timber crevices during laying. The young larvae emerge after about three to five weeks from the base of the egg. They bore into the timber.  The eggs may be visible, but the larval entrance holes are not.It is essential for the egg to attach to the wood so that the newly hatched larva can successfully penetrate the timber. If someone disturbs the eggs, reinfestation is unlikely.

Larva: –

The larva appears whitish and has fine hairs covering its body. Its head resembles a hooked crescent, with a yellowish-brown colour and dark brown jaws. It remains within the wood, tunnelling up and down the grain. It occasionally tunnels across the grain to access sapwood.  Its tunnels are circular in cross-section, each up to 2mm in diameter.  This work takes place throughout the year.

The tunnel section behind the larva contains loose bore dust and frass. Frass consists of chewed wood and faecal pellets, which can appear ellipsoidal or lemon-shaped. The bore dust has a gritty texture. A fully grown larva can reach up to 6 mm in length and has three thoracic segments, each with a pair of five-jointed legs. The larva moults several times during its development. In the spring, it matures and burrows toward the surface of the timber, creating a slightly enlarged chamber. This chamber is free from bore dust and is located just below the surface of the wood. Within this chamber, the larva transforms from a larva into a pupa.

Pupa:-

At this stage of the cycle, which lasts from two to eight weeks, metamorphosis takes place. The body tissues reorganise, allowing us to recognise a creamy-white adult shape. It has legs, wing cases, antennae, etc. These are held in thin, transparent pupal skin. It can move only the last few segments of the abdomen.

At maturity, the pupal skin bursts off, and an adult beetle is born. It spends a period of rest whilst the skin parts harden and turn brown. After this, the beetle bites its way out into the open air through the exit hole, emergence hole, or flight hole. The emerging beetle may need to navigate obstacles such as paint, varnish, and other surface coatings. Some beetles are even strong enough to chew through lead flashings.

Emergence usually occurs between May and August, with the majority occurring in June and July, though random emergences can also occur.

Adult: –

The adult common furniture beetle is 3 to 5 mm long, with larger individuals usually being female. It is reddish-brown to dark brown in colour. Its hood-shaped prothorax almost completely hides the head when viewed from above, and the angle between the hood and the wing covers is 180 degrees.

All members of the Anobiidae family exhibit various degrees of head hooding. Their two front wings have evolved into protective coverings called elytra, which feature longitudinal rows of small pits, known as punctures. Additionally, fine, short yellow hairs cover the upper parts of their bodies. Its adult beetle stage extends over two or three weeks only, during which time it does not feed. The only damage it does is in forming the exit hole.

The length of the common furniture beetle’s life cycle depends on timber species and condition, temperature, and moisture level.  Indoors, it can survive for about 3 years. However, five years is not uncommon.

Damage to timber

The damage to timber depends on the species, its growth rate, and sapwood content. Woodworm infestations rarely cause structural failure. However, concentrated infestations can lead to failure, especially in fast-growing timber with high sapwood content.

The moisture content of the timber (>15%) is the key to controlling an infestation within a building.  Some infestations are promoted in buildings due to poor maintenance.

Parasites which affect the common furniture beetle

There are some parasitic insects which feed on the common furniture beetle. For instance, Korynetes caeruleus is a member of the Cleridae family. A common predator of the Death Watch Beetle, it also attacks Anobium. The larva of this steely blue beetle grows to 14mm and moves slowly around Anobium tunnels, hunting out and devouring the wood-eating larvae.

Pediculicides venti-icosus (grain Itch-Mite) have been found living within the larval bore dust of active common furniture beetle (A.punctatum) infestation. It causes severe dermatitis in humans. This large occurrence was recorded in detail in France. Due to global warming, it could occur in the UK.

Action

It is sensible to have a suitably qualified person inspect the timber. The woodworm exit holes will remain for the life of the building, so the infestation could be 30 to 200 years old or recent. Testing for activity requires installing witness tabs, followed by long-term monitoring. Sometimes, the timbers may be treated with insecticide to control an infestation.