Weevil, a popular name for a large number of beetles, marked by the prolongation of the anterior part of the head into a beak or proboscis, generally used by the females as an ovipositor, and by both sexes as a boring organ. They were formerly ranked in one family Curculionidæ, but Le Conte constituted them a special group with the title Rhynchophora, and divided them into several families—Curculionidæ, Scolytidæ, Brenthidæ, and Anthribidæ. According to some authorities there are about 30,000 species; and most would allow at least half that number. With few exceptions the footless grubs are destructive to plants. The Curculionidæ are compact weevils, with very hard wing-covers, and with a downward-pointing beak or proboscis, bearing the antennæ on its sides and the mouth-parts at its end. Their scales are often very brilliant. With few exceptions they devour plants—roots, stems, leaves, fruits, seeds, or, in fact, any part. Among the 10,000 described species are: Calandra granaria, whose larvæ feed on stored grain; C. oryzae, attacking rice, wheat, and maize; various species of Rhynchophorus, whose large, fleshy, white larvæ, known as palm-grubs or grugru, are sometimes eaten; Balaninus, whose mandibles, unlike those of other beetles, move vertically, whose larvæ are hatched in chestnuts, hazel-nuts, acorns, and the like; Trichobaris trinotata, a little black weevil, which destroys potatoes in America; Anthonomus pomorum, often destroying apple-blossom in Britain; Conotrachelus nenuphar, which lays its eggs in nectarine, plum, apricot, peach, and other stone-fruit, and is a great pest in America; Cionus scrophulariæ, whose larvæ spin cocoons remarkably similar to the capsules of Scrophularia nodosa, which the insect usually infests; Pissodes, whose larvæ attack pines; Phytonomus punctatus, a clover weevil, introduced from Europe into America; Entimus imperialis, the diamond-beetle, with very brilliant scales. Species of the likewise brilliant Rhynchites attack fruit-trees; species of Apion especially affect vetches; and those of Larinus infest Composite.
The Scolytidæ are very small weevils, some almost microscopic, which, both as larvæ and as adults, bore in wood and bark of trees, especially Conifere, and occasionally attack herbaceous plants (see BARK BEETLES). The Brenthidæ are much elongated weevils, mostly tropical, usually infesting bark, and notable for the combats of the rival males, which are larger and better armed than their mates. Brenthus and Eupsalis are representative genera. Among the Anthribidæ Cratoparis lunatus, common in the eastern United States, feeds on the fungi of dead trees; and the larvæ of Brachytarsus are even more aberrant in their habit, for they are parasitic on female coccinsect. The seed-inhabiting 'weevils' or Bruchidæ, which do much damage to the seeds of leguminous plants, within which the larvæ hatch and pupate, were excluded by Le Conte from his group Rhynchophora, and placed near the Chrysomelidæ. Both in Europe and America Bruchus pisi, B. rufimanus, &c. are destructive to peas and beans, but the common pea-weevil in England is Sitones lineatus, one of the Curculionidæ.
The most important British weevils are probably the following: Anthonomus pomorum on apple-blossom; Apion aprieans, &c. on clover; Bruchus rufimanus on bean-seed; Hylesinus fraxini; Hylurgus piniperda; species of Otiorhynchus on vines, raspberries, strawberries, &c.; Scolytus destructor; Sitones lineatus. For preventing or lessening the attacks of these pests, see Miss Ormerod's Manual of Injurious Insects (2d ed. 1890).
See Riverside or Standard Natural History; Le Conte and Horn in Proc. Amer. Phil. Soc. (xv. 1876).