- Ptinus rufovillosum De Geer, 1774
- Anobium fatidicus Shaw, 1792
- Anobium pulsatorium Scriba, 1790
- Anobium tessellatum Olivier, 1790
- Ptinus faber Thunberg, 1784
- Ptinus fuscus Gmelin, 1790
- Ptinus pulsator Schaller, 1783
Death Watch Beetle
No status defined
Value of species
A species of woodboring beetle that sometimes infests the structural timbers of old buildings. The adult beetle is brown and measures on average 7 mm (0.3 in) long. Eggs are laid in dark crevices in old wood inside buildings, trees, and inside tunnels left behind by previous larvae. The larvae bore into the timber, feeding for up to ten years before pupating, and later emerging from the wood as adult beetles. Timber that has been damp and is affected by fungal decay is soft enough for the larvae to chew through. They obtain sufficient nourishment by using a number of enzymes present in their gut to digest the cellulose and hemicellulose in the wood.
The larvae of deathwatch beetles weaken the structural timbers of a building by tunneling through them. Treatment with insecticides to kill the larvae is largely ineffective and killing the adult beetles when they emerge in spring and early summer may be a better option. However, infestation by these beetles is often limited to historic buildings, because modern buildings tend to use softwoods for joists and rafters instead of aged oak timbers, which the beetles prefer.
To attract mates, the adult insects create a tapping or ticking sound that can sometimes be heard in the rafters of old buildings on summer nights; therefore, the deathwatch beetle is associated with quiet, sleepless nights and is named for the vigil (watch) being kept beside the dying or dead. By extension, a superstition has grown up that these sounds are an omen of impending death.
This beetle is found in Europe, including the United Kingdom, as well as North America, Corsica, Algeria, and New Caledonia. Its natural habitat is dead or decaying hardwood, or in some cases coniferous wood, especially when the timber has been softened by fungal attack. This may be due to the way fungal decayed wood effects nitrogen metabolism in the deathwatch beetle. Decayed wood is also much easier for the larva of the deathwatch beetle to bore into which allows them to develop at a faster rate. The sapwood is more nutritious and is usually attacked first, followed by heart wood that has been softened by decay. Oak (Quercus spp.) is the main host, with American oaks being more susceptible than European oaks. Pollarded willow is also attacked in the United Kingdom. The beetle does not infest wood that has recently died; about sixty years must pass for dead oak to reach a suitable condition for attack. These beetles tend to stay on the same piece of wood for several generations until resources are used up and the piece of wood is no longer sufficient.
In Britain, the adults emerge in April, May or June. The males emerge first, and the females are willing to copulate as soon as they emerge, often in the afternoon. Emergence only occurs in temperatures above 10 degrees Celsius. Mating takes place in a concealed location, mainly on surface wood, and lasts for about an hour. Females lay eggs in crevices in the wood or in the holes left by emerging beetles, The adults do not feed, and so die within a few weeks, by which time the female may have laid 40 to 80 eggs in small batches.
The eggs hatch after about a month. The newly hatched larvae are tiny and chew their way into the timber, feeding on the wood. Their growth is slow and it may take from two to ten years, or even more, for them to reach their full size. At this stage they pupate in a chamber close to the wood surface, and either emerge through a newly created hole after twenty to thirty days, or else emerge in the following spring (about eleven months later).
In buildings, deathwatch beetles infest old oak timbers, especially those that have been the subject of fungal decay, usually by the fungus Donkioporia expansa. This fungus affects damp timber, often gaining entry where rafters or joists are embedded in stone walls, or in the vicinity of leaking roofs or overflowing gutters. It is not the adult insects that cause structural damage to the building, but rather their larvae tunneling through the wood.
Wood is difficult to digest, but as long as the wood has been softened by fungal decay, the enzymes in the guts of the larvae are able to digest the cellulose and hemicellulose forming the cell walls; this enables the larvae to make use of the protein, starch and sugars found within the cells.
The steely blue beetle (Korynetes caeruleus) is a predator of the deathwatch beetle and of the common furniture beetle (Anobium punctatum). The adult female blue beetle lays her eggs in the exit holes made by the emerging borers, and the carnivorous larvae wander through the galleries made by the wood-borers, feeding on their larvae. The adult deathwatch beetles are weak fliers and may run over the surface of the timber, rather than fly. They are sometimes caught by spiders, their silk-encased husks being found on webs.
- Król Ż. Fauna koleopterologiczna Janowa pod Lwowem // Sprawozdanie Komisyi Fizyjograficznej. – Kraków, 1877. – 11. – S.33-63.