Most roundheaded and flatheaded borers are found within a structure shortly after it is built. Adult beetles that emerge inside the home often end up near lights or at a window. They do not bite or sting. Most will not reinfest structural wood, especially when it is painted, varnished, waxed or finished. The old house borer is an exception. Some adults enter homes on firewood or are attracted to home lights and accidentally gain entry.
Identification

Adult roundheaded borers vary in length from 8 to 76mm. They are elongate and usually cylindrical (some flattened) with long antennae, which give them the name 'longhorned beetles.' Beetles attacking softwoods can be drab and unattractive, whereas beetles on hardwoods are brightly colored and conspicuously marked. Larvae are whitish to cream-colored, thin-skinned, segmented and 9 to 50mm long with the head partly withdrawn.

Adult flatheaded borers are 6 to 34mm long, boat-shaped and flattened. Many are beautifully marked or metallic colored and are often referred to as 'metallic wood borers.' Wing covers are ridged or roughened. Larvae have flattened plates on the upper and lower surface of the first segment behind the head. They are whitish to yellow, with no legs and one to two inches long. Abdominal segments are smaller than thorax segments.

Redheaded ash borer, Neoclytus acuminatus (Fabricius)

An elongate, slender, cylindrical beetle, 6 to 8mm long, reddish-brown with yellow crossbands on the wing covers. The thorax bears four to six small transverse ridges on the median longitudinal ridge. Larvae feed in the unseasoned wood of hardwood trees, honeycombing the sapwood and packing mines tightly with granular frass. Primary host trees include ash, oak, hickory, persimmon and hackberry.

Locust borer, Megacyllene robiniae (Forster)

A medium-sized, robust beetle from 14 to 18mm long, black and marked with yellow crossbands. One band on the wing cover is W-shaped. The thorax is wider than it is long. Larvae feed beneath the bark and in the wood of black locust, and exude frass. In the autumn, adults are found feeding on the pollen of goldenrod. Larvae are a serious pest of black locust.

Painted hickory borer, Megacyllene caryae (Gahan)

Adults resemble locust borers. Eggs are laid in spring on bark scales of logs cut in winter. Larvae feed in freshly cut wood of hickory, osage-orange, hackberry, grape and ash; large amounts of granular frass are exuded. Hickory firewood held over the summer can be seriously riddled with adult emergence.

Ivorymarked beetle, Eburia quadrigeminata (Say)

Adults are elongate, subcylindrical, pale-yellow and 14 to 24mm long. Each wing cover has two small, longitudinal, ivory spots close together at the base; there is a second similar pair just behind the middle. The thorax has two blackish tubercles on top and a short, sharp spine on each side. Larvae are true heartwood borers, preferring dry, solid wood where it excavates large, contorted mines tightly packed with frass. Oak, hickory, ash, chestnut, maple and cypress can become infested. Beetles sometimes emerge from flooring and furniture several years after they have been placed in a building.

Elm borer, Saperda tridentata Olivier

Adults are 9 to 14mm long and densely clothed with grayish pubescence. The thorax and wings bear narrow orange stripes on the sides. The wings have three oblique crossbars. Adults lay eggs in bark of weakened or dying elm trees. Larvae bore beneath the bark, filling the mines with fibrous frass and completely destroying the inner bark and cambium. Park and shade trees are severely injured, especially old, mature, unhealthy trees. Limbs are attacked first.

Tanbark borer, Phymatodes testaceus (L.)

Adults are elongate, depressed beetles 8 to 13mm long. The thorax is rounded and yellowish with the wing covers either blue or yellowish. Larvae feed beneath the bark of dead oaks and sometimes in stored hemlock bark. Larvae can mine entirely in the bark of stored and piled wood, causing economic loss. Use bark within three years.

Rustic borer, Xylotrechus colonus (Fabricius)

Adults are dark-brown beetles up to 8 to 17mm long with irregular variable whitish or yellowish markings.

Southern pine sawyer, Monochamus titillator (Fabricius)

Adults are large, elongate, cylindrical beetles 15 to 30mm long, black to brownish-black and often mottled with whitish or grayish pubescence. The thorax is cylindrical with a spine at each side, and the antennae and legs are very long. Larvae bore beneath the bark of recently killed and felled pine, spruce and balsam fir trees by filling the mines with fibrous frass.

Blackhorned pine borer, Callidium antennatum hesperum Casey

Adults are flattened, blackish-blue beetles 9 to 14mm long with the thorax rounded and indented on each side of the middle. Larvae feed beneath the bark and in the sapwood of dry coniferous wood, making extensive mines and exuding large amounts of granular frass. Feeding occurs primarily in pines, spruces, hemlocks, junipers and cedars. Lumber sawed and stored is often injured.

Bronze birch borer, Agrilus anxius Gory

Adults are small beetles 6 to 10mm long, flattened and green-bronze in color. Larvae attack dying or weakened birches, beech and aspens. White and paper birches grown as shade and ornamental trees are injured most seriously. Larval mines are always packed tightly with fine, sawdust-like pellets or frass arranged in arc-like layers. Beetle emergence holes are D-shaped.

Control Measures

Identification of the beetle, evaluation of the extent of damage and structural characteristics of the infested building are needed to plan a control program. Since most beetles do not reinfest structural timbers, control is not needed. Most control programs are limited to temperature treatment, replacing infested wood, spot treatment with a residual insecticide or, in severe infestations, fumigation.

To prevent beetles from emerging from firewood, bring in only an amount that can be burned within three to five days. Always inspect antique furniture, picture frames and wood brought from foreign countries for evidence of emergence holes, frass, larval infestations or any other signs that might indicate an insect infestation.