Latin: Xestobium rufovillosum
If you can even talk about mastodons in the borer beetle world, then the deathwatch beetle takes first place in Denmark. The deathwatch beetle – with the Latin name Xestobium rufovillosum – is the largest borer beetle in this country.
The deathwatch beetle can make a special sound that in ancient times has given it the name “death clocks”.
Appearance
Although the deathwatch beetle is the largest borer beetle that lives in Denmark, it is still quite modest in its size. An adult beetle is only between 6 and 9 millimeters long. The beetle has a brown color, but around the body it also has sporadic spots of hair that appear yellowish and almost metallic. It is these areas of hair that give the borer beetle its characteristic speckled appearance.
An adult deathwatch beetle larva grows about 1 centimeter long. The body shape of the larva is curved, and it is generally pale. However, its head is yellow-brown, while its jaws are dark brown.
Biology and behavior
In the period from March to June, it is mating time for the deathwatch beetle, and here it is noticed by a special kind of knocking. Through 6 to 8 quick knocks – which are repeated at short intervals – the two sexes signal to each other so they can find each other. The sound is produced by the beetle hitting its breast shield against the sides of the passage in the tree.
Once the male and female have mated, the female lays her eggs. She lays about 50 eggs, which are placed in cracks, crevices, or old fly holes in the tree. When the eggs hatch, the larvae go down into the wood – which they live on – and where they continue their further development.
The deathwatch beetle does not come into being from one day to the next. In building timber, the development can often take between 5 and 10 years. There are several factors that come into play in relation to the speed of development, which among other things counts the nature of the wood, the type of wood, humidity, and temperature.
Once the larva has undergone its development, it will begin to pupate. This often happens in the month of July or August. After a few weeks in this condition, the larva is transformed into an adult deathwatch beetle. However, it does not move from its nest immediately, but stays inside the tree until the following spring, after which it gnaws out of the tree. The tree bears visible signs of the beetle’s exit. It leaves a clear round fly hole in the wood, measuring about 3 millimeters in diameter.
When it comes to finding the most optimal areas for the deathwatch beetle to settle in, it prefers various species of hardwood. But oak is the favorite. In some cases, it can also go in moisture-damaged coniferous wood. The beetle prefers wood, which in one way or another is very moist and thus has been damaged or attacked by some form of fungus.
Damage
The deathwatch beetle prefers as described oak trees. But in these times, softwood is mainly used for construction, which is why the beetle rarely poses the great risk in newer houses and buildings.
It is worse for older half-timbered houses, manor houses or old churches, which have often used oak timber in construction. And here, the deathwatch beetle can sometimes appear as an annoying pest that can do great damage.
Prevention and pest control
The deathwatch beetle attacks wood that is very moist or infested with fungus. Therefore, it is often infiltrating water or moisture that is the root of an attack from the beetles. Therefore, as a precautionary measure, gutters, downspouts, roofs, and similar areas in the building should be closely monitored.
When finding the moisture-damaged area, it is important to put a stop to the moisture. This is best done using dehumidification, ventilation, circulation, and heating. If the area is infested with deathwatch beetles, it may be necessary to combine the repair with a treatment of the wood in question. If the attack is significant, it may be necessary to replace the damaged wood. It can be an advantage to replace the wood with treated wood, such as pressure-impregnated timber. However, it is also possible to treat the wood with a wood preservative that protects the wood from both insect and fungal attacks. In hard-to-reach areas, it can be an advantage to treat with an insect powder that is distributed on the areas where the beetle moves. It will kill the beetles before they have time to lay their eggs.
"Pests in House and Home"
"Bed Bugs - Bites, Stings and Itches"
"Food Pests"
"Husets dyreliv" (Insects Around the House - Only danish)
"Skadedyr i træ" (Timber Pests - Only danish)
"Stuefluen" (Common Housefly - Only danish)