Many people refer to deathwatch beetles as wood-boring beetles. The larvae make tunnels in the wood as they eat it. Some species make a tapping sound in the tunnels. People who heard the tapping sound at night thought it was Death coming for someone in the home.
Deathwatch beetles belong to the beetle family Anobiidae. There are several species that are commonly called Deathwatch beetles. However, some people use the term for all anobiid beetles.
The beetle that is most commonly known as the deathwatch beetle is Xestobium rufovillosum (DeGeer). It is found in the eastern portion of the United States. The adult beetle is a grayish-brown insect. It is cylindrical in shape and usually less than ¼” long.
The deathwatch beetle attacks hardwood that has previously been damaged by fungus. It can attack lumber or pieces of furniture. The infestation can spread from the original hardwood item into nearby items made of softwood. It can also attack books on shelves.
The female beetle deposits eggs in cracks in the wood. When the eggs hatch, the larvae burrow into the wood to eat and grow. As they make their tunnels, the larvae pack the tunnels with their droppings, which resemble tiny bun-shaped pellets. Scientists call this material frass. There may be powder mixed with the pellets. The appearance of the frass and the density in the tunnels depends on the type of wood that is infested.
If the temperature is warm, the larvae can develop in about a year. In unfavorable conditions, the development can take up to ten years. When the larvae are fully developed, they change into adult beetles. After changing to adults, both male and female deathwatch beetles begin tapping on the sides of the tunnels.
The adult beetles make holes in the wood in order to get out. The adult deathwatch beetles make circular exit holes. The holes can vary in size, but they are usually about 1/8″ in diameter. When the adults come out of the tunnels, frass may fall out as well.
If the tapping could not be heard, the exit holes and the falling frass are often the homeowner's first clue that deathwatch beetles have been active. Many times homeowners buy pieces of furniture, especially antiques that were previously infested by deathwatch beetles. When the item is moved, frass falls out and the owner assumes the infestation is active.
If homeowners see frass falling, they should observe closely to see whether any new exit holes appear. New exit holes or tapping inside of the wood are the telltale signs that the infestation is active.
Control measures can depend on the item that is infested and the size of the infestation. If only a few pieces of lumber are being attacked, the easiest (and least expensive) approach might be to simply replace the damaged wood.
Liquid insecticide can be applied to the surface of bare wood or it can be injected into the larval tunnels. A piece of furniture can be fumigated in a special vault or chamber. Whole-house fumigation is normally only done for severe infestations.
If there are signs of deathwatch beetles, it is probably a good idea to consult a pest control professional who is licensed in that category. He or she can confirm that the infestation is active. The pest control professional can also explain the most effective and economical treatment options.