Common Name: Cerambycids, Longhorned Beetles, Roundheaded Wood Borers
Scientific Name: Various
The common name of long-horned comes from their antennae which are very long, often much longer than the body, roundheaded comes from the larvae which have a fairly cylindrical thorax and bore round to slightly oval holes in wood, and wood borers because the larvae bore through wood. With the exception of the old house borer, Hylotrupes bajulus (linnaeus), and the flat oak borer, Smodicum cucujiforme (Say), these beetled do not reinfest seasoned wood and are therefore nuisance pests, although some can cause minor/cosmetic damage by adult emergence through various materials.
About 1,200 species occur in the United States and Canada. This section will be restricted to those species which attack wood used in structures or are commonly brought into the structure in firewood.
Depending on the species, adults usually about 3/8-1″ (10-25 mm; range 2-60 mm) long; usually oblong or elongate and somewhat cylindrical, some flattened with only prothorax cylindrical. Head with compound eyes notched on inner notch so that base is partially surrounded by eye; usually 12-segmented (range 10-25+ segments). Elytra (wing covers) usually covering abdomen, a few species with short elytra. Tarsi apparently 4-4-4 (5-5-5 with 3rd bilobed and surrounding small 4th segment). Depending on the species, mature larvae about 3/8-3 1/8+” (10-80+ mm) long; body elongate, cylindrical, parallel-sided except thorax enlarged/swollen, and segments distinctly separated; color whitish or cream; ocelli 0-5 pairs; antenna short, 3-segmented; and legs absent, or very short and 5-segmented with spine like tarsus.
(1) Some leaf beetles (Chrysomelidae) with pronotum nearly always widest at front (subfamily donaciinae), or antenna short and body 1/8-1/2″ (3.2-12 mm) long (subfamilies Criocerinae and Orsodacinae), or elytra usually widest at rear and rarely over 3-/” (10 mm) long (subfamily Galerucinae).
(2) False blister beetles (Oedemeridae) with tarsi 5-5-4.
(3) False long-horned beetles (Cephaloidae) with tarsi 5-5-4 and claws comblike.
(4) Soldier beetles (Cantharidae) with tarsi distinctly 5-5-5.
(5) Cebrionid beetles (Cebrionidae) with mandibles enlarged and hind/rear angles of pronotum extended/prolonged.
Larval galleries wind irregularly below the bark with a lot of frass evident. The galleries usually extend into the sapwood (some species into heartwood) of softwoods and hardwoods. Galleries are oval, up to 1-2″ (12 mm) long diameter, and have the frass loosely or tightly packed into them. Depending on the species, frass texture varies from being rather fine and meal-like to very coarse and almost excelsior like. Exit holes are round to slightly oval, with the longer diameter 1- 8-3/8″ (3-10 mm); the longer diameter is never more than twice the height or shorter diameter. They attack unseasoned wood, both logs and lumber. They do not reinfest seasoned wood with the exception of the flat oak borer and the old house borer.
1. Flat oak borer, Smodicum cucujiiforme (Say). Adults about 1-4-7/16″ (7-11 mm) long; body elongate, narrow, parallel-sided, and flattened; color dull yellow or brownish yellow, shining, antenna darker; eyes deeply emarginate, facets large; antenna with 2nd segment less than twice as long as broad, 4th segment shorter than 3rd or 5th, reaching apical 1-3 of elytra in male, reaching midlength of elytra in female; elytra (wing covers) with apices rounded; legs with femora clavate (thickened/widened towards base), letatarsus (on posterior legs) with 1st segment about as long as 2nd and 3rd combined; flight period June to August; mature larvae about 1-2″ (12 mm) long, legs tiny, and with a smooth white triangular arch on venter of 1st thoracic segment; host trees include locust, hickory, oak, beech, hackberry, willow, and poplar; found in eastern United Stated and westward to Texas, Oklahoma, and Kansas.
2. New house borer, Arhapalus productus )LeConte). Adults about 1-2-1″ (12-25 mm) long; elongate and slender; color black, surface dull with short pale hairs/setae; eyes shallowly emarginate, not surrounding antennal base; antenna extending beyond elytral midlength with last 4 segments almost equal to length of preceeding 3 segments; pronotum slightly wider than long, sides rounded; protibia with 1 spur, metatarsal 3rd segment cleft ½ its length; flight period July to October; mature larvae up to about 1 1/2- 1 9/16″ (38-40 mm) long, color yellowish white, and segments distinctly separated; host trees include fir (Aibes spp.), pine (Pinus spp.) And Douglas fir; found in Pacific area from British Columbia to Baja California and Rocky Mountains south of Mexico.
3. Old house borer, Hylotrupes bajulus (Linnaeus).
4. Redheaded ash borer, Neoclytus acuminatus (Fabricius). Adults about 1-8-9/16″ (4-15 mm) long, elongate, tapering towards rear; color reddish brown with elytral apical 3/4 darker, with yellow markings consisting of 4 transverse bands, 1 basal, 1 oblique before middle, 1 behind middle, and 1 on apical 1/3; antenna 11-segmented, outer segments slightly thickened/enlarged; elytra with apices obliquely truncate, angles acute or somewhat spine like (subspiniform); flight period May to August in north, February to November in south; attacks many hardwoods; found in eastern United States and west to Colorado, eastern Canada west to Manitoba.
5. White spotted sawyer, Monochamus scutellatus (say). Adults about 1-2-3-8″ (13-35 mm) long; elongate, rather slender, subcylindrical; color black or dark brown, somewhat shiny, and often bronze, with white markings consisting of dense white pubescense (short fine hairs/setae) on scutellum (subtriangular area between elytral bases), dorsal surface with sparse irregular gray and white pubescence appearing in 3 rather indistinct transverse bands; eyes deeply emarginate, upper lobe small; antenna long, greater than body length in females and twice body length in males, scape (1st segment) robust and with scarlike structure (cicatrix) at apex; pronotum with 1 prominent spine like tubercle on each side; scutellum with rear margin broadly rounded; elytra finely punctuated (punctured) at base and apex rounded to suture (middle elytral junction); front legs of male elongate; flight period April to September; hosts are characteristically pines (Pinus spp.) But in northern part of range are also common in spruce (Picea spp.) And fir (Aibes spp.) Found in Alaska to Newfoundland, southward to California and Arizona in the west and southward to northern Florida in the east.
Females lay their eggs in wood or bark crevices during the spring, summer, or early autumn. Eggs are laid singly or in small groups. Larvae hatch in a few days. After finding a suitable entry point, they feed near the surface at first where the protein is in greatest concentration. As they grow, they bore deeper into the wood. The larval stage may last from a few months to several years, being prolonged by a low nutritional value of the wood and any decrease in moisture such as caused by the wood being sawed into lumber.
Pupation takes place in a cell near the wood surface. The time of adult emergence depends on the species and environmental conditions. Outside, they mate, lay eggs, and die. Indoors, the only 2 species that can reinfest dry, seasoned wood are the old house borer and the flat oak borer. The new house borer requires at least 2 years to complete its life cycle (adult to adult), the old house borer at least 3 years, the flat oak borer 1-2 years, and the pine sawyers (Monochamus spp.) Require 2 years in the more northern parts of their range.
Flat oak borer larvae bore tunnels in the dry heartwood of oak and sometimes other hardwoods. The tunnels are about 1/16′ (2 mm) in long diameter and are tightly packed with fine, granular frass. Larvae may continue to feed in the wood until it is mostly consumed. Exit holes are slightly oval and about 1-16″ (1.6-2 mm) in long diameter. Attacked are seasoning and newly seasoned sapwood and heartwood or hardwoods, primarily oak. Flat oak borers can infest or reinfect dry/seasoned wood in structures. They have been a problem in log homes. New house borer females lay their eggs only in deep bark crevices.
Therefore, seasoned wood with the bark removed, such as lumber, is not reinfected but there can be a problem with log homes. Larvae first feed between the bark and sapwood, later tunnel in the sapwood, and finally tunnel into the heartwood. The tunnels are tightly packed with fibrous frass. These beetles attack dead and dying pines and furs, especially Douglas fir, and they are particularly abundant in trees of burned-over areas. Adults emerge mostly within 1 year of construction of homes/structures. Only larvae which are almost mature can survive the drying conditions of lumber; the rest die.
Emerging adults will chew through any material covering the infested wood, such as hardwood flooring, linoleum, plasterboard/sheetrock, composition roofing, etc. The larger larvae make rasping noises as they feed. As a mater-of-fact, this is the source of the common name of sawyer. Log homes present special problems. This is because bark is often left on the logs, especially around knot-holes, the logs are often either green or air-dried at the time of construction, design flaws allow the logs to increase or retain a high wood moisture content, the homes are constructed in wooded areas, and the logs are often to rigorously maintained with preservation and sealer. This situation often allows for a series of species of roundheaded wood borer infections which can start before the trees are cut/felled and progress through advanced stages of wood decay.
For adults emerging from firewood brought indoors, remove the firewood to the outside and bring it in just before burning. There is no threat of infestation except form the flat oak borer which is uncommon in firewood. Rarely is fumigation justified except in cases of widespread infestation, incessant larval chewing noises, and/or peace of mind. For reinfecting species, such as the old house borer and sometimes the flat oak borer, fumigation is often the appropriate control measure. For non-reinfecting species occurring in low numbers, the damage from emerging adults is not structural but cosmetic.
The usual procedure is to fill the exit holes with appropriate wood dowels or plaster and finish to match. Linoleum and floor tile will often require replacement and roofing usually requires patching. Log homes often require fumigation but this should be done in conjunction with correction of the conducive moisture conditions and followed by proper maintenance procedures. It is usually desirable to make an appropriate application of boron-containing pesticides to reduce reinfection and retard wood decay before the logs are sealed. All exit holes should be sealed after the boron application but before the sealer application.