Wood-boring beetles include several families of beetles whose larvae feed on wood and wood products. Wood-boring beetles play an important ecological role by tunneling through dead and decaying wood to aid in decomposition. Some wood-boring beetles feed on living, dying, diseased, burned, damaged, or dead trees but do not attack harvested lumber. These species can cause problems when the adults emerge from lumber in new construction or are carried indoors in firewood. Other species of wood-boring beetles may infest wood before and after it is milled, finished and installed; they may also infest furniture and other wooden objects.
Wood-boring beetle adults lay eggs in the cracks and crevices of exposed wood. When these eggs hatch, larvae bore into the wood, producing tunnels as they feed and pack frass behind them. While adults who have emerged from wood may only live a few days or weeks, the destructive larvae often spend 2 to 5 years boring through wood.
Adults: The adult beetles are elongate, cylindrical, reddish brown to brownish black, moderately glossy, without dorsal pubescence. They range from 6 to 13 mm long and 2 to 3.5 mm wide. The head is not visible from above, as it is recessed beneath the pronotum. The pronotum is strongly convex, quadrate, arcuately emarginate in front, the sides with broad tooth-like projections on anterior one-half, converging to plate-like sculpture on the central area It is strongly deflexed on the apical half, with the posterior angles projecting.
The elytra are nearly tubular in shape until the posterior 1/10 where they abruptly descend to the abdomen. This area, called the apical declivity, is somewhat excavated and variable between the sexes; the males possess two incurved, hook-like projections (not seen in the female) as well as an additional smaller, highly variable, tubercle near the sides. The surface is densely, deeply punctate, with the punctures arranged in fairly distinct rows, but somewhat variable in shape and extent, especially near the apical declivity.
The larva is white to yellowish, with a characteristic bostrichid shape, variable in size with most last instars averaging 10 mm. The mandibles are black, conical and the darkest area on the larva. The setation is sparse and pale, and not readily visible to the unaided eye. The antenna is shown in the figure below. The epipharynx possesses posterior projections and a characteristic setal pattern. The maxilla is shown in the figure below.
All stages are found in dry lumber which is eaten by the adults and larvae. The life cycle in Florida has not been studied, but in India it is as follows (Beeson & Bhatia 1937):
The eggs are deposited on rough surfaces of sawed lumber and logs, in holes, cracks or short tunnels made by the female. The larval borings may be 1/4 inch wide, winding for several inches. The tunnels are usually filled with tightly packed, fine, sawdust-like material which is characteristic of this genus. Tunnels of most pinhole and shothole borers contain very little such material. Pupation occurs in a cell at the end of the tunnel. The adult emerges through an exit hole, often after chewing through a few inches of wood. Length of development from egg to adult is variable from one to six years. Apparently they can survive under dry conditions present in manufactured wood products and emerge several years later, as do some of the Cerambycidae.
Wood borers as pests
Wood boring beetles most often attack dying or dead trees. In forest settings, they are important in the turnover of trees by culling weak trees, thus allowing new growth to occur. They are also important as primary decomposers of trees within forest systems, allowing for the recycling of nutrients locked away in the relatively decay-resilient woody material of trees. To develop and reach maturity wood boring beetles need nutrients provided by fungi from outside of the inhabited wood. These nutrients are not only assimilated into the beetles’ bodies but also are concentrated in their frass, contributing to soil nutrients cycles. Though the vast majority of wood boring beetles are ecologically important and economically benign, some species can become economic pests by attacking relatively healthy trees or by infesting downed trees in lumber yards. Species such as the Asian longhorn beetle and the emerald ash borer are examples of invasive species that threaten natural forest ecosystems.
Wood boring beetles are commonly detected a few years after new construction. The lumber supply may have contained wood infected with beetle eggs or larvae, and since beetle life cycles can be one or more years, several years may pass before the presence of beetles becomes noticeable. In many cases, the beetles will be of a type that only attacks living wood, and thus incapable of “infesting” any other pieces of wood, or doing any further damage. Genuine infestations are far more likely in areas with high humidity, such as poorly ventilated crawl spaces. Housing with central heating/air-conditioning tends to cut the humidity of wood in the living areas to less than half of natural humidity, thus strongly reducing the likelihood of an infestation. Some species will infest furniture.
Some beetles invade wood used in construction and furniture making; others limit their activity to forests or roots of living trees.