Deathwatch Beetles

Dorcatoma

Side view of Hemicoelus

Hemicoelus or enclosing head. Antennal club 3- or 4-segmented, loose. 2-20 mm. (1 western species to 2 in.).

Bostrichids are wood borers, and attack living trees, dead twigs and branches, or dry seasoned timber. The adults of one unusual western species bore into the lead sheathing of telephone cables, allowing moisture to enter the cable and causing a short circuit; this insect, Scobicia declivis (LeConte), is called the Short-circuit Beetle (normally lives in wood and does not feed when it bores into cables). The giant of this family is the Palm Borer, Dinapate wrighti Horn, which occurs in California; it is about 2 in. long.

PSOID BEETLES Family Psoidae

Identification: Similar to Bostrichidae (p. 189), but head not bent down, visible dorsally. Mandibles large and strong. 6-28 mm.

These beetles occur in the West, where they bore into the heartwood or branches of various trees and shrubs. Some severely prune trees and are very destructive to orchards in Oregon and California.

POWDER-POST BEETLES Family Lyctidae

Identification: Form distinctive: narrow, elongate, flattened, head visible dorsally. Antennal club 2-segmented, abrupt. Reddish brown to black. 1-7 mm.

The common name refers to their habit of boring into seasoned wood and reducing it to powder. Lyctids are very destructive to dried wood and wood products of various kinds, including woodwork, timbers, tool handles, gunstocks, and other manufactured materials.

Superfamily Scarabaeoidea

Terminal antennal segments extended laterally into a club of various types, usually lamellate, sometimes flabellate. Tarsi 5-5-5.

Mostly moderate-sized to large.

STAG BEETLES Family Lucanidae

Identification: Elongate-robust. Antennae elbowed, club 3- or 4-segmented, segments of club not capable of being held together in a tight ball. Black to reddish brown. Mandibles of cf very large, sometimes branched. Pronotum without a median groove. FW usually smooth. 8-40 mm.

Most adult stag beetles feed on sap flows; larvae live in decaying logs and stumps and apparently feed on juices of rotting wood (larva of 1 species feeds in sod). The greatly developed, sometimes branched mandibles of the males of a few species give these beetles their common name. Adults of most species are

BESSBUGS 191

found on the ground in woods, others on sandy beaches. Adults of a large reddish-brown eastern species frequently fly to lights at night.

BESSBUGS Family Passalidae

Identification: Elongate-robust, parallel-sided, black and shiny. Head with a forward-directed horn. Pronotum with a distinct median groove, FW with longitudinal grooves. Antennae not elbowed, segments of club not capable of being held together in a tight ball. Pronotum and FW distinctly separated at sides. 30-40 mm.

Only 1 of the 3 U.S. species of bessbugs, Popilius disjunctus

(Illiger), occurs in the East; the other 2 occur in s. Texas. The eastern species forms colonies in well-decayed logs and stumps and is fairly common. Both adults and larvae stridulate; the sounds produced probably serve as a means of communication. Bessbugs have a number of common names, including patent-leather beetles, betsy-beetles, and horned passalus beetles. Despite their size and strong mandibles, the passalids do not bite.

SCARAB BEETLES Family Scarabaeidae See also Pl. 7

Identification: Oval or elongate, usually stout and heavy-bodied, varying greatly in form and size. Antennae 8- to 11-segmented, lamellate (rarely flabellate), segments of club capable of being held tight together. 2-50 mm.

This is one of the largest families of beetles, with nearly 1300 N. American species. Many are very important because of damage done by larvae or adults. There are 14 subfamilies in N. America, of which only the most important are discussed here.

Dung Beetles and Tumblebugs, Subfamily Scarabaeinae (see also PI. 7). Hind legs situated closer to tip of abdomen than to middle legs; hind tibiae usually with only 1 apical spur. These beetles occur in or near dung, manure, and carrion. Tumblebugs {Canthon and Deltochilum) are dull black (some are green), about 20 mm. or less, without horns, and the hind tibiae are rather slender; a pair will form a mass of dung into a ball, roll the ball a distance, dig a hole, and bury it; then the female lays eggs in it. Males of some dung beetles (like Phanaeus) bear horns on both head and pronotum, or on either.

Aphodian Dung Beetles, Subfamily Aphodiinae. Members of this group have the hind legs closer to tip of the abdomen than to middle legs, and hind tibiae bear 2 apical spurs. They are usually smaller and more elongate than Scarabaeinae. Apho-diines are quite common in cow dung. Adults are generally black, sometimes with the front wings red or yellowish.

Earth-boring Dung Beetles, Subfamily Geotrupinae (not illus.). The body is very stout, convex, and shiny, and the antennae are 11-segmented. Adults and larvae are found in cow dung, horse manure, carrion, fungi, and under logs. The most common species (Geotrupes) are 14-20 mm. and black (often with a purplish luster) or brownish.

Subfamily Acanthocerinae (not illus.). Black, round, 5-6 mm., the middle and hind tibiae dilated and spiny. These beetles can bend head and prothorax downward and roll themselves into a ball. The 3 U.S. species, which are not common, occur from the eastern states to Texas. They are found under bark and in rotting logs and stumps.

Skin Beetles, Subfamily Troginae. These beetles are dull brownish, the dorsal surface is roughened or tuberculate, and the 2nd antennal segment rises before tip of the 1st. They are usually

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