Roundheaded Borers belong to the the family Cerambycidae, which includes many species of large woodboring beetles, where adults usually have very long antennae that is much longer than the body. Because of that feature, these beetles are commonly called "longhorned beetles." All adult cerambycids have large, strong, toothed mandibles. The larvae are somewhat cylindrical, and have a large cylindrical thorax, resulting in burrows of a similar shape in the infested wood, hence the name, "roundheaded borers." The larvae have small heads, but powerful mandibles. Larval legs are lacking or vestigial.

There are two very important roundheaded borer beetles that attack wood in buildings: the Newhouse Borer (Arhopalus productus) and Oldhouse Borer (Hylotrupes bajulus).

Other common Cerambycids

Any insect that infests old, weakened, or fire- or insect-killed trees is likely to be incorporated into buildings constructed from lumber obtained from such trees if it is not kiln-dried. Among such insects are many species of cerambycids.

Wharf Borer (Nacerdes melanura) is a beetle that resembles a cerambycid. It is found throughout much of the United States and Canada, particularly in coastal areas, along lake shores, and along major inland waterways. The larvae may be found in moist timbers, such as wharf timbers, foundation pilings under buildings, in damp cellars or crawl spaces, in wood around leaky faucets, in buried wood, or in any wood that is damp or soggy, and particularly if it is decayed. In England, it has been found in timbers of many barges and wooden-hulled ships sailing in the region of the Thames estuary. In London, the adults have been seen by the "tens of thousands, running over the pavements of the Strand" without their origin being discovered. It is not known if wharf borer larvae damage sound wood. They are pests primarily because the adults may suddenly emerge in a building in large numbers and gather around windows, doors, or other sources of light, and thereby become nuisances.

The Nautical Borer (Xylotrechus nauticus) is a western species, 8 to 15 mm long, and varies in color from grayish brown to nearly black. It has 3 transverse, zigzag white lines on the elytra, and rather short antennae for a cerambycid. The larva is robust in form, and may attain a length of 18 mm. In California, the larvae may be found in live oak, black oak, and sometimes in eucalyptus and madrone, or in walnut or stone-fruit trees in orchards. It is most frequently encountered in the home emerging from firewood cut from such trees.

The Spotted Pine Sawyer (Monochamus maculosus), may reach a length of 3 cm or more, with antennae 2.5 times the length of the body. These beetles are brown, with bluish-gray dorsal spots. The prothorax has a prominent median tooth on each side. The larvae are very destructive to both heartwood and sapwood of dying, fire-scorched, and recently felled pines in the western states.

The (Ergates spiculatus) is one of the most conspicuous and best-known species found in lumber. It is a large, slender beetle, 4.5 to 6 cm long, reddish brown, with head and thorax darker than the elytra. The lateral margin of the prothorax is armed with a few large and many small, sharp spines. The adults are often attracted to lights. The creamy-white larvae are 5 to 7 cm long. E.spiculatus not only attacks the wood of recently killed or felled trees, but also fallen logs, stumps, and power and telephone poles and has often ruined fire-killed Douglas fir before salvage operations could begin. This species occurs throughout western North America.

The Fourspotted Longhorn (Eburia quadrigeminata) is a common eastern species on hickory, locust, and ash, often attracting attention in resort areas. It is 1.5 to 2.5 cm long, light brown to tan, and easily recognized because of the 2 pairs of elevated, ivory-colored swellings on, and the 2 spines at the tip of, each elytron. The life cycle usually requires 2 years, but this species has also been found emerging from flooring, sills, and other wood members 10 to 15 years after the materials were installed.

The Banded Alder Borer (Rosalia funebris) is one of the best-known and most attractive of the Pacific Coast cerambycids. It is 2.5 to 4 cm long, marked with black and white, and has very long antennae that are annulated with black and white. It breeds in ash, alder, and California laurel and, east of the Sierra Nevada, generally in willow. This species is responsible for the hollowing-out of the trunks of many of the larger laurel trees in California. It is mentioned here mainly because of its conspicuous and striking appearance, resulting in many requests for identification. However, during periods of very high temperatures, the beetles are attracted to recently painted dwellings after the paint has become dry, apparently attracted to certain volatilized ketones from the paint. They are present on some buildings in such large numbers as to be a definite nuisance.

The Black Pine Sawyer (Monochamus scutellatus) is 1.6 to 3 cm long and shining bronzy black, with a white scutellum, coarsely punctured, a large median "tooth" on each side of the prothorax, and very long antennae, often twice the length of the body. It is widely distributed in the coniferous forests of North America, and is especially abundant in timber following burns.

The Black Timberman (Monochamus oregonensis), ranges from British Columbia to southern California and east into the Rocky Mountain states, sometimes causing losses to fir logs exceeding 10 to 20% if they are left in the woods a few months. This species is 2.5 to 4 cm long, and has a cylindrical, deeply and coarsely punctured body. The color is uniformly black, sometimes with a bronzy reflection, and the scutellum is white. Silvery-white spots are sometimes scattered over the elytra and on the thorax and antennae.

Various species of Neoclytus likewise commonly emerge from firewood and are found in homes. This genus is characterized by the many transverse carinae (elevated ridges) on the disk of the pronotum. The antennae are relatively short, as in Xylotrechus, but are more or less clubbed, and the legs are long. Unlike the larvae of Xylotrechus, which have no legs, those of Neoclytus have small legs composed of at least 2 segments. Probably the most common species of Neoclytus on the Pacific Coast is N. conjunctus. It has either white or yellow markings on a black background. The pronotum is broadly rounded, the elytral apices are rounded, ancl the head, thorax, and abdomen are hairy. It breeds in Oregon ash, various white oaks, madrone, manzanita, eucalyptus, pear, and apple. Any of these trees cut for lumber should be utilized promptly, otherwise the larvae of N. conjunctus will render the wood useless for anything but firewood. Even the value of the infested timber as firewood is reduced because of the honeycombing of the wood by these beetles. Cordwood should be piled and covered with brush, for shaded wood is not attractive to the beetles.

In the eastern United States, two species of Neoclytus that emerge from firewood and are sometimes found in houses are N. acuminatus and N. caprea. Neoclytus acuminauts is 6.5 to 18 min long, reddish brown, with 4 yellow bands across the elytra, and long, reddish legs. It attacks unseasoned wood with bark remaining, and frequently causes serious losses of ash, hickory, and oak logs left exposed during the flights of these insects. Neoclytus caprea is 12 to 15 mm long, deep purple, with 3 yellow bands across the elytra and 3 narrow, yellow bands across the prothorax. This species sometimes destroys an entire winter clut of ash logs, honeycombing the sapwood with tunnels that are tightly packed with granular frass.