Primitive Weevils

Superfamily Curculionoidea

Head prolonged into a more or less distinct snout. Tarsi 5-5-5, usually apparently 4-4-4.

PRIMITIVE WEEVILS Family Brentidae Identification: FW elongate and parallel-sided. Prothorax pear-shaped. Head with a long or short straight beak. Femora stout, toothed. Antennae threadlike or beadlike. Dark brown to blackish. FW with orange marks. 7-30 mm.

Adults of this group are found under bark and in worm-eaten wood, where they feed on fungi, the sap from tree wounds, or wood-eating insects. Larvae are wood borers.

FUNGUS WEEVILS Family Anthribidae

Identification: Robust, elongate to oval. Usually brownish and often mottled with patches of white, gray, straw-colored, brown, or black pubescence. Beak short, broad. Antennae clubbed, not elbowed. Pronotum often with sharp lateral margins posteriorly. 1-11 mm.

Adult anthribids are usually found on dead twigs and branches, under bark, or on fungi (generally woody fungi), and are not common. Most are good fliers and some jump. Larvae live in plant materials on which adults are found. The eastern species most often encountered is Euparius marmoreus (Olivier), which is 3.5-8.5 mm. and brown mottled with patches of white, black, ashy, and brown pubescence. Adults and larvae are found on poly pore fungi.

SNOUT BEETLES Family Curculionidae See also Pl. 8

Identification: Snout usually well developed. Antennae clubbed and nearly always elbowed. Palps small and rigid, often concealed within mouth. Labrum absent. 1-35 mm.

This is one of the largest families of insects (over 2500 N. American species), and its members are common. Practically all are plant feeders; large numbers are serious pests of cultivated plants. Many snout beetles chew holes in fruits, nuts, and other parts of the plant. Adults often bear pubescence or scales, and frequently play dead when disturbed. From N. America 42 subfamilies are recognized, only a few of which can be mentioned here.

Subfamily Cyladinae (Pl. 8). Antlike, 5-6 mm. Pronotum reddish, FW blue-black. Antennae not elbowed, last segment long, swollen. Our only representative of this group is the Sweetpotato Weevil (PL 8), Cylas formicarius elegantulus (Summers), a pest of sweet potatoes occurring in the South.

Subfamily Apioninae. Black or gray. 1.0-4.5 mm. Somewhat pear-shaped. Antennae not elbowed. Trochanters elongate. Larvae bore in seeds, stems, and other parts of various plants (chiefly legumes); adults usually occur on foliage.

Subfamily Baridinae (not illus.). Part of thoracic pleura (mesepimera) visible from above between prothorax and FW. This is the largest subfamily of snout beetles (about 500 N. American species). Several are important pests.

Broad-nosed Weevils, chiefly Subfamilies Leptopiinae, Bra-chyrhininae, and Thylacitinae (see also Pl. 8). Beak short, quadrate, often widened apically, usually with 1 or more longitudinal grooves. Mandibles large, with a small cusp that breaks off and

BROAD-NOSED, ACORN, & NUT WEEVILS 203

leaves a scar. Antennal scrobe (groove in beak into which basal antennal segment fits) only vaguely defined. Most species are flightless because the elytra are grown together or the hind wings are reduced. White-fringed beetles (Graphognathus, Thy-lacitinae) are important pests in the Southeast, where they feed on many cultivated plants; they reproduce parthenogenetically, and no males are known.

Acorn and Nut Weevils, Subfamily Curculioninae. Snout slender and very long, as long as body or longer. Femora with a stout triangular tooth. Eyes often partly covered by prothorax.

BOLL WEEVIL SNOUT BEETLE

(Anthonominae) (Apioninae)

NOsIcTwEEVILS (Brachyrhininae) (Thylacitinae)

FW with narrow scales. Larvae develop in the fruit of various nut-producing trees.

Subfamily Anthonominae (see also p. 203). Antennae elbowed and clubbed, rising near apex of snout, the basal segment fitting into a well-defined scrobe (groove in beak into which basal antennal segment fits). Front coxae contiguous, located in about middle of prothorax. Snout fairly long, not fitting into a pro-sternal groove at rest. An important pest in this group is the Boll Weevil (illus., p. 203), Anthonomus grandis Boheman (about 5 mm., yellowish brown), which does much damage to cotton; adults feed on the seedpod (boll) and lay eggs in the feeding hole; larvae feed inside the bolls and eventually destroy them. This is a large subfamily, with about 200 N. American species.

Subfamily Cryptorhynchinae. Beak at rest fits into a groove in prosternum. Antennae elbowed and clubbed. Eyes oval and partly covered by prothorax when beak is in prosternal groove. FW usually wider than prothorax, giving the insect a broad-shouldered appearance. The Plum Curculio, Conotrachelus nenuphar (Herbst), is a common species and a serious pest of stone fruits; injury results from both adult and larval feeding.

Billbugs and Grain Weevils, Subfamily Rhynchophorinae. Antennae rise near eyes, the basal segment not fitting into the short scrobe (groove) and extending past posterior margin of eye. 6 antennal segments between basal segment and club; 1st segment of antennal club enlarged and shining. Pygidium (last dorsal abdominal segment) usually exposed. Members of this group are 3-31 mm. Some of our largest snout beetles belong to the group. Billbugs are large snout beetles that feed on grasses; larvae bore in stems and adults feed on foliage. Grain weevils (Sitophilus) are brownish and 3-4 mm.; they attack stored grain and are often serious pests.

PINHOLE BORERS Family Platypodidae

Identification: Very elongate-slender, parallel-sided. Brownish. Tarsi long, slender, 1st segment long. Head visible dorsally, as wide as or slightly wider than pronotum. 2-8 mm.

Pinhole borers attack trees, and their burrows extend deep into the heartwood; adults and larvae feed on a fungus in the burrows. These beetles usually attack weakened or unhealthy trees, and often bore into felled logs. Adults occasionally fly to lights. The group is small, with only 7 species in N. America.

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