weevil, common name for certain beetles of the snout beetle family (Curculionidae), small, usually dull-colored, hard-bodied insects. The mouthparts of snout beetles are modified into down-curved snouts, or beaks, adapted for boring into plants; the jaws are at the end of the snout. The bent antennae usually project from the middle of the snout. The largest weevils are about 3 in. (7.6 cm) long, with the average length being about 1/4 in. (0.6 cm). The snout varies greatly in length among the different species; in the curculios, or nut weevils, it may be longer than the body. Different weevil species attack different parts of plants—fruits, seeds, leaves, stems, or roots. In most species the female lays her eggs inside the plant tissue, on which the growing larvae feed. The granary weevil and rice weevil are serious pests of stored cereal grains. The thousands of other destructive weevil species include the sweet-potato, vegetable, alfalfa, clover leaf, strawberry, and pine weevils, as well as the cotton boll weevil, the most serious weevil pest in the United States. The seed weevils, including the bean weevil, are not true weevils, but boring beetles of another family; they feed on leguminous crops, such as peas and beans. Weevils cause millions of dollars' worth of damage annually. The bark beetles, or engraver beetles, are related to the weevils. True weevils are classified in the phylum Arthropoda, class Insecta, order Coleoptera, family Curculionidae.

boll weevil or cotton boll weevil, cotton-eating weevil, or snout beetle, Anthonomus grandis. Probably of Mexican or Central American origin, it appeared in Texas about 1892 and spread to most cotton-growing regions of the United States. Over the years the weevil became a significant pest, destroying about 8% of the annual U.S. cotton crop. Boll weevil devastation was a major reason for diversification of the South's historic cotton economy. In 1978, however, the U.S. Dept. of Agriculture began a concerted eradication campaign. By the end of the century the weevil had disappeared from from most of the nation except Texas, Louisiana, and Mississippi, where the campaign continued.

The young adult is grayish, darkening with age, and about 1/4 in. (6 mm) long, with a long snout for boring into the cotton boll, or seed pod, where weevils feed on the cotton fibers. Weevils may also invade cotton flower buds before they mature into bolls. Females lay eggs within the bud or the boll, where pupation (see insect) occurs. The larvae eat the entire contents of the boll. Metamorphosis from egg to adult takes about three weeks; from 2 to 10 generations occur each season. The weevil's resistance to some poisons, and the removal of some poisons from the market, have encouraged Integrated Pest Management, e.g., the use of safer insecticides, synthetic growth regulators, and pheromone traps, and the release of sterile males to frustrate reproduction. Adults are also controlled by elimination of field litter, especially cotton stalks, in which they overwinter. Short-season cotton, bred to mature early, escapes much damage from weevil larvae.

The boll weevil is classified in the phylum Arthropoda, class Insecta, order Coleoptera, family Curculionidae.

bean weevil, common name for a well-known cosmopolitan species of beetle (Acanthoscelides obtectus) that attacks beans and is thought to be native to the United States. It belongs to the family Bruchidae, the seed beetles. The bean weevil is small, about 1/6 in. (0.4 cm) long, and stout-bodied, with a short broad snout and shortened wing covers (elytra). The adults attack legumes either in storage or in the field and may even completely destroy them. The grubs, or larvae, hatch from eggs laid in holes that have been chewed by the female into stored beans or into pods in the field. In heavy infestations there may be two dozen or more newly hatched larvae in one bean. When full-grown, the larvae form pupae in the eaten-out cavity. As many as six generations are produced in a single season, and in storage breeding continues as long as there is available food left in the beans and a warm temperature. The larvae can be killed by fumigation or by heating the seeds to 145°F; (63°C;) for two hours. Bean weevils are classified in the phylum Arthropoda, class Insecta, order Coleoptera, family Bruchidae.

or snout beetle

Any of about 40,000 beetle species in the largest family of beetles, Curculionidae, which is also the largest family in the animal kingdom. Most weevils have long, elbowed antennae that may fold into special grooves on the prominent snout. Many species are wingless. Most species are less than 0.25 in. (6 mm) long, are plainly coloured and marked, and feed exclusively on plants. Some species are more than 3 in. (80 mm) long. The larvae may feed on only a certain part of a plant or a single plant species; adults are less specialized. The family includes many destructive pests, including the boll weevil.

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Small beetle (Anthonomus grandis) found almost everywhere cotton is cultivated. It is the most serious cotton pest in North America. Adults vary in size according to how much food they received as larvae, but they average about 0.25 in. (6 mm) long, including the long, curved snout. In the spring adults deposit eggs in cotton buds or fruit. After hatching, the larvae live within the cotton boll, destroying the seeds and surrounding fibres. Because the larvae and pupae remain inside the cotton bolls, they cannot be killed with insecticides. The boll weevil destroys an estimated three to five million bales of cotton annually.

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