Lyctidae

Adult powderpost beetles are 2-7 mm long, reddish brown to black, and subcylindrical with a slightly prominent head which is constricted behind the eyes. Antennae are 11-segmented and claviform. The mandibles are well chitinized, broad at the base, and bidentate at the tip. Elytra have punctations and fine setae. Larvae limit their feeding to hardwoods, and feed on the sapwood of various hardwood species. Larvae utilize the starch, sugar, and proteins in wood, but they cannot digest the cellulose and hemicellulose in the cell walls.

Round emergence holes 2-3 mm in diameter and small amounts of powdery frass are characteristic of lyctid infestations. Frass usually falls from emergence holes and accumulates in small piles. Lyctid frass is fine and feels soft and not gritty when rubbed between the fingers; the frass of anobi-ids has a gritty texture. Lyctids attack oak, hickory, and ash, but other infested hardwoods include walnut, pecan, poplar, sweetgum, wild cherry, and several species of tropical hardwood. Bamboo, which is a grass, is often attacked because of its high starch content. Lyctids prefer the seasoned sapwood portion ofhardwoods, and wood with moisture content between 8 and 32%, but the greatest activity occurs in wood with 10-20% moisture. They usually do not lay eggs in wood with a starch content less than 3%. In air-dried lumber much of the starch content is consumed in respiration by the ray cells, which remain alive for some time after cutting. Kiln drying kills the ray cells so that the starch content is fixed within the sapwood, and the wood is susceptible to lyctid attack for many years.

Oviposition takes place 2-3 days after mating, usually in the afternoon and early evening. Before oviposition adult females bite and perhaps chew a small amount of the wood to determine its starch and moisture content. The female extends her long, flexible ovipositor directly into vessels and pores of the wood. A preliminary examination of the vessel is made with the pygidial palps of the ovipositor, and further examination of the vessel is made by the vaginal palps. One or more eggs are deposited longitudinally in the vessel. Egg-laying usually lasts 1-2 weeks, with most of the eggs laid 7-8 days after mating. The diameter of the vessels in hardwood can be a limiting factor in lyctid infestations. They must be large enough to accept the ovipositor and the eggs. The average diameter of the ovipositor of Lyctus brunneus is 0.078 mm, and of L. linearis is 0.083 mm. Hardwoods with vessel diameters larger than this are subject to infestation. Softwoods are not infested since the exposed tracheids will not accept the Lyctus ovipositor. Examples of susceptible wood include a variety of temperate hardwoods, but beech and birch are not usually infested. Tropical wood infested includes obeche, agba, afara, mahogany, iroko, seraya, meranti, teak, and keruang.

Eggs are translucent white and cylindrical, with rounded ends. Eggs of L. brunneus are 0.8-1.25 mm long and 0.150.175 mm wide. Eggs typically have a threadlike process at the anterior end. Hatching occurs in 6-7 days at 26 °C, and 19-20 days at 15 ° C. After leaving the egg chorion, the larva is generally facing the opening of the vessel. The larva feeds for a short time at the opening, thenittunnels into the wood. Larval food is the starch in the cells of the wood; the cell wall is not digested. Besides starch, certain sugars and protein are present in the larval food. First-stage larvae are white and straight-bodied, and with a pair of small spines at the posterior end. Larvae have a curved form and a slightly enlarged thoracic region after the firstmolt. Early-stage larvae usually tunnel with the grain of the wood; later stages have stronger mouthparts and tunnel at irregular angles. They are negatively phototropic and eat away from the wood surface. Full-grown larvae are usually less than 5 mm long. At this stage in development, they tunnel close to the surface of the wood and prepare a pupal chamber immediately below the surface. The pupal period lasts 12-30 days.

Adult beetles cut through the pupal chamber and surface of the wood to emerge, and a small amount of frass is expelled from the tunnel. During the day beetles remain in cracks and crevices in the wood and in the emergence holes, but become active atnight; they fly and are attracted to light. The life span of the female is about 6 weeks, and males live 2-3 weeks. Development from egg to adult takes 9-12 months, but takes 78 months under favorable conditions of moisture and starch content of the infested wood. In warm regions, there are two head and mandibles are visible from above. Full-grown larvae are 5-7 mm long, yellowish white and with a distinct pair of enlarged and dark spiracles visible near the posterior end. The emergence hole is 1-1.8 mm diameter. Egg-laying takes place 2-3 days after copulation, and usually occurs at night. The female has a very long and slender ovipositor, and uses it to locate a vessel in the sapwood. During egg-laying the insect can bend the ovipositor 90°; typically 1-3 eggs are laid in each vessel selected. Fecundity is about 80 eggs. Hatching occurs in 19-20 days at 15 °C, 14-15 days at 20 °C, and 7-8 days at 26 °C. Larval developmentis 8-10 months, depending on environmental conditions and the wood infested. Larvae tolerate wood moisture content between 8 and 30%, and development is optimum at 16% moisture content and 25 °C. Full-grown larvae bore approximately 3 mm from the wood surface and form a pupal chamber; the pupal period lasts 12-21 days. Development from egg to adultis iyear in unheated premises or outdoors, but extends to 2-4 years under adverse conditions. Emergence of adults takes place from May to September, with a peak in July in the UK. The adults are active flyers and are attracted to lights at night. Parasites of this species include Eubadizon pallidipes (Braconidae), Sclerodermus domesticus, S. macrogaster (Bethlyidae), Tarsostenus univittatus (Cleridae), and Teretrius picipes (Histeri-dae). This lyctid probably originated in North America, but it is now distributed around the world.

Shiny powderpost beetle, Lyctus cavicollis (Fig. 5.14c) Adults are 2.5-5 mm long and reddish to rust brown. The prothorax has the anterior portion narrower than the combined bases of the elytra. Adults closely resemble L. planicollis, but are distinguished by the slender antennal segments, and the oval and small antennal club. The antenna is large, and the club is prominent in L. planicollis. This species is widespread throughout North America.

Small powderpost beetle, Lyctus discedens Adults are 36 mm long, and brown to dark brown. Full-grown larvae are about 5 mm long, and yellowish white. Emergence holes are 1.5-2.0 mm diameter. This species is one of the major wood-infesting beetle pests in Australia, and it infests and reinfests sapwood of hardwoods.

European powderpost beetle, Lyctus linearis Adults are 3-7 mm long and dark brown, with glossy elytra. It resembles L. cavicollis in size and color, but can be distinguished by having single, rather than double rows of punctations of the elytral striae, and by its prominent frontal lobes. L. linearis is commonly encountered in commercial hardwood products, especially in seasoned hickory, oak, ash, and walnut. It occurs in eastern USA and in Europe. Parasites of this species include Eubadizon pallidipes (Braconidae), Tillus unifasciatus, and Mono-phylla terminata (Cleridae).

Southern powderpost beetle, Lyctus planicollis (Fig. 5.13a; 5.14d) Adults are 4-6 mm long and black to blackish brown. Prothorax has a broad, shallowmedian depression, and the ely-tral striae are separated by rows oflong setae. Full-grown larvae are 3-5 mm long and yellowish white. This species is found throughout the USA and Mexico. The parasites reported for this species include Hecabolus lycti, Monolexis lycti (Braconidae), and Tarsostenus univittatus (Cleridae),

Tropical powderpost beetles, Minthea rugicollis, M. reticulata (Fig. 5.13f; 5.14e) Adults are 2.0-3.0 mm long and the body is uniformly brown. The antenna has the terminal segment slightly longer than the preceding segment. Abdominal stern-ite 5 of the female has a fringe of fine setae on the apical margin, but this fringe is absent on males. The emergence hole is 1-1.5 mm diameter. Minthea rugicollis and M. reticulata cause considerable damage to hardwoods in the tropics, and appear in imported hardwoods in some temperate-region countries. They attack seasoned and green timber of kempas, mernati, pulai, and seasoned rubberwoodinMalaysia. Damageis distinguished from Lyctus species by the small size of the emergence holes. Parasites reported for this species include Monolexis spp., (Braconidae), Cephalonomia spp., Sclerodermusspp. (Bethylidae), Cercocephala spp. (Pteromalidae), and Tarsostenus univittatus (Cleridae).

Parallel powderpost beetle, Trogoxylon parallelopipedum (Fig. 5.13c; 5.14f) Adults are 2.5-4.2 mm long, reddish brown to brown, and with fine yellowish setae on the body that give it a velvety appearance. The prothorax lateral edge is straightand appears parallel. Adults are capable ofrapid movement. It infests ash, hickory, and oak timbers, and bamboo. The winter is spent in the larval stage, and adult emergence and egg-laying occur in spring. Adults of the second generation emerge in late summer or fall. Developmentis completed in 4-5 months in recently sawed logs. Parasites reported from this species include Monolexis lycti (Braconidae), Sclerodermus domesticus, and S. macrogaster (Bethlyiidae). This species occurs in the USA and the UK.

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