For this instalment of our woodworm series, we look at the House Longhorn Beetle (Hylotrupes bajulus). This beetle is also known as the Camberley beetle, because its main area of distribution in the UK is North-West Surrey. It is common in Europe from Norway as far east as Siberia and down to North Africa. It has even been introduced to Australia, South Africa and the United States via infested timber and finished products.
Sightings increased in the early 20th century as timber quality decreased and sapwood quantity increased. At one point House Longhorn Beetles were commonly found in orange crates coming from Spain, and more recently, in Pitch Pine coming from the South of France.
In this piece we’ll discuss the House Longhorn Beetle’s characteristics, why they may appear in your property and what you can do to treat or prevent it from causing havoc in your home.
The House Longhorn Beetle has some distinctive features that set it apart from others in the ‘woodworm’ family. Most notably, the long antenna (horns) found on most Longhorn Beetles that give them their name.
Another distinctive characteristic includes a white spot on each wing case and the two black spots surrounded by long hairs found on the thorax, which give the appearance of an owl’s bald face.
They are usually 7-25 millimetres long and the female is larger than the male. They can either be brown or black in colour. They rarely fly in the UK as they require temperatures of 25-30°c, so they get around your property by walking.
In warm weather, the adult female produces pheromones to attract a mate. Attracted to softwood timbers by terpene vapour, she uses her ovipositor to lay small clutches of eggs in a fan shape within shrinkage cracks in the timber surface. On average 140 eggs are laid over 12 days. The resultant larvae bore long straight galleries within the sapwood for 3-6 years (max 11 years), before the adult emerges through a 6-9mm oval hole. This happens in hot weather between July and September.
Where can the House Longhorn Beetle be found?
In the UK, House Longhorn Beetles only attack the sapwood of softwoods (Pine, Spruce, Fir), but in Europe it will attack the sapwood of hardwoods (Oak, Alder, Poplar). They appear to require hot conditions to thrive, although cold in winter may also be important. For this reason most infestations are found in the roof space of properties and often in timbers on the South facing side of the roof.
As large larvae (25mm long and 7.5mm wide), it does not take many to cause significant damage. In fact, they can be heard gnawing if it is quiet. There will be few flight holes, so the damage is often not visible until they have removed the entire sapwood band, then the outer surface becomes rippled and sausage shaped frass spills out as the surface ruptures.
Treatment and Prevention
House Longhorn Beetles became such a problem in some areas that Building Byelaws were introduced in 1962 requiring softwood roofing timbers to be pre-treated with preservative to protect them from attack. These Byelaws are now Part A 2B2 of more recent Building Regulations.
In order to protect your property from a potential House Longhorn Beetle infestation, there are several steps you can take:
Keep timber dry – the optimal temperature for larval development is 28-30°c and 26-50% moisture content, so keeping timber dry can aid protection from egg laying
Keep timber protected – once in the timber, larvae can develop at 10% moisture content, which is at the lower limit of average levels in properties of 9-15%, so you will want to prevent the beetles from gaining access in the first place
If the worst happens and an infestation appears, professional fumigation is one possibility, provided the property is isolated and suitable for treatment. This should only be undertaken by experts with a license to carry out the fumigation procedure. You should take time to speak to a pest expert to establish a bespoke plan for your property, to ensure that your home is spared from any further potential damage.
Forest Longhorn beetles
There are at least 26,000 species of Longhorn beetles in the world. These occur naturally in UK Woodland, but more commonly in tropical forests. Different species attack the sapwood of softwoods or hardwoods or in some cases both. This is why it is important to know the species of timber and country of origin of an infested object.
The tropical Forest Longhorn’s can emerge from timber many years after it has been converted into furniture and arrived in the UK. The larvae tend to be large and this helps them to survive quite harsh conditions. It also means they can often be heard rasping away inside what appears to be solid timber. Emergence holes are usually elliptical or banana shaped.
Within the UK, the most common call out to properties is for the Oak Longhorn or Tanbark borer (Phymatodes testaceus). These beetles lay their eggs under the bark of recently felled hardwood logs or dead standing trees. They continue development for two years and usually emerge from May to July. If however the logs (predominantly oak) are brought inside for the fire, the larvae can be tricked into emerging earlier. This can lead to lots of scurrying and the appearance of dozens of beetles that congregate on window cills. The adult beetle is 8-13mm and occurs in two colour forms, yellowish brown and deep blue black, often with a rust coloured thorax. They cannot re-infest building timbers or the logs as these are now too dry, so should be released outside.
You don’t have to live with the problem if you do spot House Longhorn Beetles. If you suspect you have an issue, or have found beetles emerging from timber in your home, then we suggest you should take a look at our treatment pages to discover how our woodworm experts can help you.
Next month’s blog will be our final in our 2021 woodworm series for Peter Cox. Stay tuned as we focus on identifying and treating another pest, the Bark Beetle!