Wood, in its natural state or as part of human structures, serves as a habitat for various insects. This material provides both sustenance and shelter. While some wood-dwelling insects are harmless, others can cause significant damage to timber and wooden objects. Understanding these insects and their habits is important for identifying potential issues.
Common Wood-Dwelling Insects
Among common wood-dwelling insects are termites, social insects living in colonies. Subterranean termites, prevalent in many regions, live in soil and build mud tubes to access wood above ground. These termites are typically creamy-white workers, about 1/8 inch long, and consume softer wood portions, often leaving a layered appearance. Their reproductive swarmers are usually dark brown to black, up to 1/2 inch long, with two pairs of wings of equal length.
Drywood termites, unlike subterranean counterparts, do not require soil contact and infest dry, seasoned wood directly. Often found in coastal areas, they are larger, ranging from 1/4 to 3/8 inch in length, with swarmers that can be reddish or light brown. Instead of mud tubes, drywood termites create small “kick-out” holes to expel fecal pellets, known as frass, which resemble small, hard grains. They consume wood across the grain, creating smooth, erratic galleries.
Carpenter ants are another notable wood inhabitant, differing from termites as they do not consume wood. These ants, black or red and black, are larger than many other ant species, with workers ranging from 1/4 to 1/2 inch long. They excavate galleries within wood to create nests, preferring moist or decaying wood to establish colonies. Their distinguishing features include a constricted waist and elbowed antennae, unlike termites’ straight antennae.
Powderpost beetles encompass several families, all known for reducing wood to a fine, powdery dust.
True Powderpost Beetles (Lyctidae)
Lyctidae, or true powderpost beetles, are slender, reddish-brown to black, 1/16 to 1/4 inch long, primarily infesting hardwoods with large pores like oak or hickory. Their frass is very fine and powdery, similar to talc, and not gritty.
Death-Watch or Furniture Beetles (Anobiidae)
Anobiidae, known as death-watch or furniture beetles, are cylindrical, brown to black, 1.5 to 9 mm. They attack both hardwoods and softwoods, and their frass may feel gritty.
False Powderpost Beetles (Bostrichidae)
Bostrichidae, or false powderpost beetles, also bore into wood, typically having cylindrical bodies 1.5 to 9 mm long, often with a hood-like pronotum covering their head. These beetles infest both hardwoods and softwoods, and their frass can vary from fine to coarse.
Wood Borers
Wood borers, such as the old house borer, are beetles whose larvae tunnel through wood. The larvae are creamy-white and C-shaped; adults create distinct exit holes upon emergence. Old house borers make oval-shaped exit holes in structural lumber.
Why Insects Inhabit Wood
Insects inhabit wood for reasons tied to their survival and reproduction. For some species, wood serves as a primary food source. Termites and powderpost beetle larvae, for instance, digest cellulose in wood for nutrients. Wood type and condition, such as moisture or starch levels, influence which insects are attracted for feeding.
Wood also provides a secure environment for shelter and nesting. Carpenter ants, while not consuming wood, tunnel into it to create elaborate galleries where they raise young and expand colonies. These excavated spaces offer a stable habitat, shielding them from predators and environmental fluctuations. The internal structure of wood provides an ideal matrix for constructing intricate nests, creating a microclimate that helps regulate temperature and humidity.
Moisture content within wood is another attractant for many insects. Species like subterranean termites and some anobiid beetles are drawn to damp or decaying wood, as it provides humidity for their survival. Moisture can soften wood, making it easier for insects to bore through and establish homes. This dampness supports conditions required for their life cycles.
Signs of Wood-Dwelling Insect Activity
One common indicator of wood-dwelling insect activity is frass, a mixture of wood fragments and insect excrement. Frass appearance varies by insect; powderpost beetles produce fine, powdery frass, while carpenter ants leave coarser, sawdust-like material. This substance often accumulates in small piles below exit holes or in wood cracks.
Exit holes are another clear sign, appearing as adult insects bore out of the wood after maturing. These holes differ in size and shape by species; powderpost beetles typically leave small, round holes, 1/16 to 1/8 inch in diameter. Wood borers, such as old house borers, create larger, oval-shaped holes, and carpenter ants can leave irregular, larger openings.
Subterranean termites construct mud tubes, pencil-sized tunnels made of soil, wood particles, and saliva. These tubes serve as protected pathways between their underground colonies and wooden structures, commonly found along foundations or in crawl spaces. Their presence is a strong indication of an active subterranean termite infestation.
Visible damage to wood can signal an infestation. This includes wood that sounds hollow when tapped, or sections appearing blistered or showing signs of internal tunneling. Termite-damaged wood can appear layered, while wood excavated by carpenter ants often has a clean, sandpaper-like appearance within their galleries. In severe cases, wood may crumble or collapse under pressure.
Audible sounds can indicate active insect presence. Faint rustling, clicking, or rasping noises from within walls or wooden structures may suggest the chewing activity of larvae, particularly from wood-boring beetles. These sounds are often more noticeable in quiet environments.
The appearance of swarmers, winged reproductive insects, or their discarded wings, is a significant sign of an established colony. Termite swarmers emerge during specific seasons to establish new colonies, often leaving piles of shed wings near windowsills or light sources. The presence of these winged forms indicates a mature infestation.