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A number of different insects can emerge and enter the home from firewood especially if the wood has been left sitting indoors for an extended period of time. Quite often these insects are woodboring and bark beetles and become especially abundant around lights and windows to which they are attracted. Certain flies and carpenter ants can also invade the home from firewood, however, since these and other insects may also originate from other situations in the home, proper identification of the insect in question is required to help determine their source. A few of the insects should be collected in a small plastic pill container or a similar tight container and brought in to the Insect & Disease Laboratory for identification, along with a brief description of where they are occurring.

Most of the insects emerging from firewood are primarily a nuisance and pose no threat to the home. The species which pose the greatest threat of infestation are the carpenter ants and powder post beetles.

The following are some of the kinds of insects apt to be occurring in and around firewood:

Woodboring Beetles

A number of different families of beetles can occur either as grubs and in some instances adults in the mines they bore in the wood or just underneath the bark of standing and felled trees. The grubs or larvae are usually fleshy white or whitish yellow and can vary considerably in size and shape depending on the family. The location and shape of the mines also varies and is characteristic to each species. Bark beetle grubs, for example, are curved and are about 1/8 of an inch and usually mine between the bark and the wood where they engrave patterns which are characteristic to each species. The adult bark beetles, which are usually small and reddish brown to black, emerge through holes made in the bark. One species, the eastern ash bark beetle, may emerge in fantastic numbers from ash firewood. Roundheaded borer grubs have cylindrical tapering bodies and can be one inch or more long when fully grown. These grubs bore into the wood of the tree, some of the tunnels being the diameter of a pencil. The adults vary in size and color and may be up to 1" long with antennae as long or longer than the body. Many other beetle families also tunnel in weakened living and felled trees.

Powder Post Beetles

Powder post beetles are a particular group of insects which bore in dead wood which can become a problem in the home if conditions are right. Both the small brownish-black beetles and the whitish grubs bore throughout the wood and reduce the wood to a fine flour-like powder over a period of time. The presence of small pinholes in the bark of the wood (from pin-sized to pencil lead sized holes) and the presence of flour-like powder may indicate the presence of these insects. Less destructive bark beetles show similar signs but the bark beetles form the characteristic galleries along the surface of the wood beneath the bark whereas the powder post beetles do not but rather bore throughout the wood. All woods are subject to the attack of powder post beetles but hardwoods, especially birch, seem to be favored. Powder post beetles and carpenter ants need relatively high moisture levels to develop.

Carpenter Ants

These are large black ants which chew out extensive galleries in dead or unsound wood in which to live and raise their young. They don't actually feed on the wood, but push out the chewed coarse sawdust pieces out of the nest area through 1/4 inch wide nest openings. The accumulation of coarse sawdust next to such openings in the wood is one of the characteristic signs of their presence. They are regular inhabitants of wooded areas where their occurrence in dead trees and limbs plays an important role in returning dead wood to the soil. Once indoors on infested wood, the individual ants may make forays to the kitchen and other areas of the house in search of food and water. The role of these ants in the home is discussed in more detail in a separate information sheet.


A variety of flies and fly-like insects can originate from firewood. The most common of these are several species of tiny black flies which are usually attracted to windows and other light sources upon emerging from the firewood. The fly larvae usually occur on and underneath the bark where they feed on decaying organic matter and fungi.

Parasitic Wasps

Certain fly-like insects which are parasites of woodborers can also emerge from firewood. Unlike flies, these have 2 pairs of wings instead of 1 pair and may bear resemblance to wasps to which they are related.

Miscellaneous Insects and Related Organisms

A variety of insects and related organisms including springtails and sowbugs which are common in the ground litter and under debris occasionally occur underneath the loose bark of firewood especially damp pieces that were on the ground. Springtails are small wingless grayish insects approximately 1/8 of an inch long that have a forked muscular appendage at the end of the abdomen which when suddenly released enables them to jump into the air. Sowbugs, relatives of insects, are gray, approximately 1/4 of an inch in size and have 7 pair of leg-like appendages. Both of these are associated with excess moisture and extensive organic debris and/or mold and shouldn't survive in a heated building. They may survive in a wet or damp basement for a period of time, however, this is not often a problem.

Various stages of different insects which normally overwinter on tree trunks can sometimes enter the home on firewood. For example egg masses of certain moths such as the gypsy moth are normally attached to the bark of trees, and once indoors under ideal conditions these may hatch releasing up to a few hundred tiny caterpillars. Cocoons and pupal stages of other insects may also be brought in this manner.

An occasional mosquito may appear in the home from firewood. One species of mosquito in particular commonly overwinters beneath loose bark. This species can bite! Fortunately they will not breed in the home.

Prevention and Control

The best method of controlling insects that are in the process of emerging from the firewood is to remove the infested firewood from the home. It is usually not necessary or desirable to treat the firewood with insecticides. Flies and other insects that are gathering around windows and lights may be vacuumed and immediately disposed of out-of-doors. Most species (with the exception of carpenter ants and powder post beetles) do little actual harm in the home and are primarily a nuisance.

Future infestations can be prevented by not storing firewood in the home over extended periods of time. Firewood should be burned within one or two weeks of its introduction in a heated area of the home. Larger supplies should be stored where it can be kept cold to prevent insects from developing and emerging. This will also reduce development of molds in the home associated with larger damp volumes of firewood.

Maine Forest Service - Forest Health and Monitoring Division
April 2000