Longhorn beetle - danger in the attic

Longhorn beetle - danger in the attic

the essentials in brief

  • If you discover a roebuck infestation, you should report it to the building authority immediately - there is an obligation to report
  • The longhorn beetle betrays itself through heaps of wood dust at the foot of the infested furniture
  • Thermal control is the most environmentally friendly, for example with heat in the oven or the sauna or with cold in the garden when the temperature is below zero
  • Combating with chemical agents is not recommended and is less efficient

Recognize infestation through damage images

Longhorn beetles are able to severely damage the wood used in conifers in a very short time. In Germany the house buck is considered to be the most dangerous wood destroyer in the house, which is why in some federal states an obligation to report has been stipulated in the building regulations. If you discover an infestation, you should contact the responsible building authority immediately.

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When building a house, choose wood with a minimum heartwood content of 90 percent. This is neither attacked by the house buck nor by the woodworm.

Signs of infestation

The feeding activity of the longhorn beetle is much more difficult to detect than damage caused by the woodworm (Anobium punctatum). The house buck clogs wood passages with sawdust and excrement so that no telltale piles of wood flour are left behind. These corridors will not be re-entered.

In the event of severe infestation, a thin wooden skin remains that can be easily scratched off and reveals the duct system. The only external distinguishing feature of infected wood are oval exit holes of the adult beetles. These are between four and seven millimeters in size. Eating noises are a clear indication of an active infestation.


Track down the billy buck with search dogs

Since 2008, trials with sniffer dogs have been carried out in Australia, which are intended to detect an infestation by the billy goat early on. To this end, two Labrador dogs were specifically trained. Their fine sense of smell should make it possible to recognize the beetle larvae in the wood up to three years earlier. Conventional measures by searching built-in wood only provide reliable information when there are already escape holes for adult beetles. Then these can already have reproduced and laid new eggs.

Assessment of an infestation

ram beetle

Before control measures are initiated, the infestation must be checked and ensured by a specialist. The roebuck is not always an option as a pest for feeding marks in wood. Other insects also leave corridors in roof beams.

Wood age and exposure

During an infestation control, the intensity of the infestation and the age of the wood of the undamaged beams are checked. Statistically speaking, it is very unlikely that timber around 60 years old will be attacked. This means that wood protection applied later does not bring any benefit.

The attractiveness of the wood species is very strong in the first 30 years and then steadily decreases. Wood is hardly endangered after 100 years and 140-year-old timber is only attacked in rare exceptions. However, infestation cannot be completely ruled out, even with old wood. If the males only find impregnated wood, they also place their scent marks on untypical old wood. In addition, fresh repair wood can increase the attractiveness again.

The older the wood, the less likely it is to be infested. However, this is not completely excluded.

Beware of dubious experts

It is not uncommon for companies to take advantage of the ignorance of the public and carry out senseless or overpriced control measures. There are often so-called door-to-door sales, in which residents let themselves be taken by surprise by self-appointed experts and sign contracts out of concern.

In some cases the infestation is so severe that the advertised control methods are no longer effective and the entire roof structure has to be replaced. Many measures are also pointless if the infestation has already disappeared or is only very weakly developed. Expensive control measures are rarely offered, even if wood damage was caused by other harmless insects such as the wood wasp or the disc buck.


In the case of a positive control, different measures are taken depending on the intensity. Often the pests are fought with chemical means. Contact insecticides are not always the best solution as they make it difficult for pests to reach. Effective control takes place in the hot air process through high temperatures. Smaller objects can be heated in the sauna. In a microwave with a built-in horn radiator, the wood can be irradiated and overheated for several minutes, so that all living creatures that contain water are killed.

Chemical control:

  • Chilling and impregnating the wooden surfaces
  • pressurized or pressureless injection
  • Fumigation with sulfuryl fluoride


To kill all life in the wood, you should heat the piece of furniture to 65 degrees Celsius for one to three hours. Proteins in the body start to coagulate at around 60 degrees Celsius, so that the organism dies.


ram beetle

The longhorn beetle, incorrectly called the longhorn beetle for short, belongs to the longhorn family. As such, the beetle can be recognized by its long antennae, which are slightly bent backwards. Because of this typical feature, the family got the common German name. The species Hylotrupes bajulus is behind the longhorn beetle. Loosely translated, this species name means something like "who drills in the wood of the bearer". This expression indicates the beetle's way of life.

A beetle with many names:

  • Girder
  • House buck
  • Big woodworm

Typical characteristics

Adult beetles are between eight and 26 millimeters long. The body is comparatively flat. Color and drawing can vary between individuals. The basic color is brown to black, with legs and antennae usually appearing a little lighter. The entire body is covered with fine and grayish shimmering hair. In some animals the elytra clearly show two pairs of white hair spots. These can be more or less intensively developed.


Longhorn beetles have a strongly rounded pronotum with two shiny calluses on the upper side. The pronotum is significantly wider than the head. The thickened thighs of the legs, the claws of which are provided with small teeth, are striking. For a longhorn beetle, the house longhorn has comparatively short antennae, with the third antenna element being longer than the fourth.


House longhorn beetle larvae can reach a length of 30 millimeters. Its ivory-colored body is clearly articulated and ends in a larger head with powerful mouthparts. There are three pinpoint eyes next to the milling tools. If they are not disturbed, their noises, which are caused by scraping off the wood fibers, can be clearly heard. They can be used as a sure sign of wood infestation. At the slightest disturbance, they stop eating and fall silent.

Way of life and development

The beetles are looking for partners between May and August, and they only live to be around four weeks old. During this time the house billy goat does not eat any food. Since it is a dry wood insect, the beetles lay their eggs exclusively in dried and mostly built-up wood.

Wood search

Immediately after hatching, the females start looking for a suitable place to lay their eggs. It uses the escaping aerosols to assess the suitability of different types of wood. Males also look for a suitable and protected area in the wood that is suitable for mating. They then produce a sexual attractant to attract females willing to mate. However, these are also influenced by the fragrance intensity of the woods. In this way, the females try to find the wood that offers optimal development opportunities for their offspring.


Two to three days after mating, the female lays eggs. These are laid in small cracks in wood through a flexible laying tube. Even the smallest gaps with a width of 0.3 millimeters are sufficient.

Six to eight clutches, each containing an average of 50 to 60 eggs, are formed during egg laying. In total, females can lay between 140 and 200 eggs. Individual females produce more than 500 eggs. Males die shortly after mating, while females die after laying eggs.

ram beetle

Development cycles

The larvae eat their way deeper into the wood shortly after hatching. They go through several growth cycles between which they molt, whereby the duration of larval development is influenced by various factors.

After the last larval stage, pupation occurs just below the surface of the wood. The larva goes through a metamorphosis and hatches as a sexually mature beetle. It usually takes four to six years for the larva to develop into an adult beetle. If the larvae live in nutrient-poor woods, the development can extend to twelve and in rare cases to 18 years.

This influences the larval development:

  • Nutrients : high protein content is important
  • Humidity : ideally between twelve and 30 percent
  • Temperature : Optimal between 28 and 30 degrees Celsius
  • Type of wood : preferably softwood such as fir, pine or spruce

Species of longhorn beetle

The European longhorn beetle is easy to recognize and can hardly be confused with other species. The biggest misunderstandings arise from misleading naming of different species. Occasionally, the misnomer, common longhorn beetle, appears. This name probably originated from a mixture of the longhorn beetle species and the longhorn beetle from the longhorn family. There are a number of other longhorn beetles that appear as pests.

scientific namefurther namesdamageDetect
Asiatic longhorn beetleAnoplophora glabripennisAsian longhorn beetleDeciduous and fruit treesblack with light spots
Chinese longhorn beetleAnoplophora chinensisCitrus longhorn beetleDeciduous trees, preferably citrus plantsblack with light spots
Common longhorn beetleStictoleptura rubraRed rascalSoftwood, preferably spruce and pinebright red-brown
ram beetle


Longhorn beetles only attack conifers such as pine and spruce, fir and larch or Douglas fir. Hardwoods secrete substances that kill the larvae. These feed mainly on the sapwood, which is in the outer areas. Occasionally they undertake exploration tours to the inner heartwood. However, this is largely avoided. The reason for this behavior is the nutritional content of the wood. The nutrient content in the outer annual rings is significantly higher than in the heartwood. The lower the protein content, the slower the larvae develop.


The distribution area of ​​the longhorn beetle extends over the entire Palearctic. The wood pest was brought to North America, South Africa and Australia by humans. Females lay their eggs exclusively in dead conifers so that their larvae can benefit from the nutrient-rich sapwood. The beetles are often found in the wood used in roof trusses or wooden facades, as these are the ideal conditions for development. Often there are already eggs in the firewood or in the firewood, so that the pests can be introduced easily.

frequently asked Questions

What does the house billy look like?

The wood pest belonging to the longhorn beetles has a variable body that can be more than two centimeters long. Its relatively short, backward-curved antennae are typical. The beetle is brown to black in color and hairy. Sometimes white hair spots can be seen on the wings. The thickened thighs are another distinguishing feature.

Can you confuse the longhorn beetle?

Mixing up the adult beetles is almost impossible, as all other longhorn beetles look different. The ash-gray evening buck (Trichoferus holosericeus, synonym: Hesperophanes cinereus) is sometimes referred to as a wood buck double. This species was brought in from warm climes and only colonizes deciduous trees. Adult beetles can be identified by their coloration. This doppelganger has a reddish-brown basic color, which is, however, masked by the intense gray to whitish hair. As a dry wood insect, this species also causes damage to the wood.

How do I recognize an infestation by the longhorn beetle?

Infestation often goes unnoticed until the first exit holes are visible on the wood. Then the larva may have already caused great damage. The first sign of an infestation are the feeding noises coming from the bars. They are reminiscent of the scratching and scraping that occurs when the edges of the thumb and middle fingernail are rubbed together. Some bulges can be seen on the wood surface.

You should pay attention to:

  • paper-thin wood layer can be easily scratched off
  • Corridors filled with dusty sawdust emerge
  • typical corrugation on the aisle walls

Why do the noises of the house buck larvae fall silent when disturbed?

The larvae are extremely sensitive to noise, because one of its natural enemies is the woodpecker. This looks for its food by knocking on the wood and looking for insects and larvae. House billy larvae fall silent at the slightest disturbance so that no predator becomes aware of them.

How can I prevent an infestation by the roebuck?

Choose native wood species that are resistant to attack by the longhorn beetle. Heartwood from larch, pine and Douglas fir, which has a maximum proportion of ten percent sapwood, ensures optimal prevention. In the same way, crack-free dry timber protects against infestation. If you cannot do without spruce or sapwood-rich softwood lumber for reasons of cost, you should treat it with a chemical wood preservative before installation.

How to protect wood:

  • Do without heat-storing wooden formwork
  • Wooden structures must be well ventilated
  • do not wall in wood to avoid the accumulation of moisture
  • do not dry laundry in the attic
  • Close attic hatches during flight time