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Woodworms

Woodworms belong to the coleoptera group of species, which are characterised for being larval-cycle insects. They share the common characteristic of feeding off wood during their larval period. The biological cycle of woodworms begins when the females lay their eggs in the cracks, grooves and holes of the wood's surface. From the eggs emerge small larvae that bore into the wood in order to feed themselves, in turn creating galleries that reduce the wood's resistance. The time during which the larvae remain in the wood depends in the species in question -ranging from several months to more than ten years. It is during this phase that the larvae damage the wood.

Towards the end of their life-cycle, the larvae position themselves close to the wood's surface and create an isolated chamber in which they transform themselves into pupae. The metamorphosis process continues until
they become winged, adult insects. The adult then breaks the chamber and the fine layer of wood separating it from the surface and ventures out. The females then lay eggs within the wood. The exit holes in the wood's surface indicate that at least one generation of woodworm have inhabited the piece. Certain species feed off the wood of leafy trees, whilst others feed off conifers. There is a third group which indistinctly attack both type of tree.

The main coleopteran xylophagous present in Spain and responsible for attacking building wood are as follows: Anobiidae (commonly known as woodworm), Cerambycidae (longhorn beetles), Lyctidae (moths), Curculionidae (snout beetles) and Bostrichidae.

Damaged caused to wood by Woodworm

 

Anobiidae (woodworm)

Anobiidae, commonly known as woodworm, are small coleoptera measuring some 3 to 11 mm in length in adulthood. Characteristically, they attack old furniture and structural elements. Some species feed on conifer wood, whilst others eat the wood of leafy trees. They generally affect the waney edge and have a preference for a certain degree of humidity. Their presence is frequently accompanied by that of rot fungi.

The larvae may grow from 3 to 5 mm in length. The round exit holes are usually between 1.5 and 4 mm in diameter, depending on the species. The duration of the larvae's biological cycle varies from between 8 months to several years, with a 2-3 year average. The species most commonly found in Spanish constructions are Anobium punctatum De Geer and Xestovium rufovillosum De Geer.

Cerambycidae (longhorn beetles)

The insects belonging to the Cerambycidae family are the largest xylophagous insects existing in Spain. Commonly known as longhorn beetles, they are to be found in wooden structures and roofs. The insect's exit holes are easy to spot in old pieces of furniture, even in those cases in which the attack is inactive. In general terms, they only attack the waney edge, thus resulting in minimum damage to pieces with a high heartwood content. Certain species feed on conifers, whilst others attach leafy trees.

The species most commonly found in Spain are Hylotrupes bajulus L., Hespherophanes cireneus VIII and Ergates faber L. The first of these species, which is most frequently found in conifers, usually attacks dry wood (of between 10 and 14% humidity), and is particularly fond of roof structures. The larva, which may grown up to 30 mm in length and 6 mm in diameter, is a silvery-white colour. It creates oval-shaped galleries which follow the grain, are blocked with sawdust and which have marks or strias along their walls. The sawdust is coarse, cylindrical and remains in the interior, given that the galleries are closed-off by a thin film of wood which the larvae leave intact.

The adult cerambycidae reach from 10 to 20 mm in length (certain species may reach up to 50 mm). The elliptical exit holes measure some 6 to 12 mm in diameter. The length of the life cycle varies between 2 and 10 years.

 

Damaged caused to wood by Longhorn Beetles

Curculionidae (snout beetles)

Detected in construction wood in Spain some twenty years ago. Its attacks are easily confused with those of the anobiidae.

Three species have been identified in Spain in wood installed in old buildings: (Pselactus spandix H., Hexarthrum exiguum B. and Amaurorrhinus bewickianus W.).

The damage they cause is very similar to that of the anobiidae. They attack the waney edge of leafy and conifer wood. In the event of previous attacks by fungi, the heartwood may be affected. Longhorn beetles require wood with 20% or more humidity.

Both the larvae and the adult insects create circular galleries similar to those of the anobiidae in the waney edge of the wood. They produce sawdust which is similar to that produced by the anobiidae, although somewhat finer and more varied in aspect.

The circular exit holes generally measure from between 1 to 2 mm in diameter. The biological cycle is varies between 1 to 2 years, depending on the species. The adult insects measure between 3 and 5 mm in length.

   

Damaged caused to wood by Longhorn Beetles

Bostrichidae

These insects mainly feed off the waney edge of the wood from leafy trees (mainly tropical) high in starch and somewhat humid. The most damaging species registered in Spain is Apate Capuchina L., which attacks leafy, boreal trees (chestnut, elm and oak).

The insects create circular galleries of between 3 to 6 mm in diameter. They create a fine, cream-coloured sawdust which is similar to flour in appearance and remains lodged in the interior of the galleries. The adult insects measure between 4 and 6 mm in length. The exit holes measure between 3 to 6 mm in diameter. Given the characteristics of their attacks, they may be confused with lyctidae (moths), although this second group creates smaller exit holes (1 to 2 mm). They have a biological cycle of approximately 1 year.

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