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WEEVIL

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Originally appearing in Volume V28, Page 468 of the 1911 Encyclopedia Britannica.
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WEEVIL , Anglo-Saxon wifel, a See also:

term now commonly applied to the members of a See also:group of See also:Coleoptera termed the Rhyncophora. This group is characterized by the prolongation of the See also:head into a rostrum or See also:proboscis, at the end of which the mouth, with its appendages, is placed. The antennae are usually elbowed, and often end in a See also:club-shaped swelling. The basal portion of the antennae frequently lies in a depression at the See also:side of the rostrum, and this gives the antennae the See also:appearance of emerging See also:half-way along the rostrum. The mouth appendages are small; the mandibles, however, are stout. The palps are very See also:short and conical as a See also:rule. The See also:body is usually small; in shape it varies very much. The elytra are very hard, and in some cases fused with one another, rendering See also:flight impossible. The larvae are See also:white, fleshy, apodal grubs, with a See also:series of tubercles along each side of the body; the head is See also:round, and bears strong jaws, and sometimes rudimentary ocelli. They are exclusively phytophagous. The Rhyncophora embrace four families,—(1) the Curculionidae, or true weevils, (2) the Scolytidae, or bark-beetles, (3) the Brenthidae, (4) the Anthribidae. The Curculionidae See also:form one of the largest families amongst the Coleoptera, the number of See also:species described exceeding 20,000, arranged in '1150 genera.

The antennae are elbowed, and clavate, with the basal portion inserted in a groove. The third tarsal See also:

joint is generally bilobed. Over 400 species exist in See also:Great See also:Britain, few of which exceed half an See also:inch in length. The genera Phyllobius and Polydrosus include some of the most beautiful See also:insects found in Britain—their brilliancy, like that of the See also:Lepidoptera, being due to the presence of microscopic scales. The See also:diamond See also:beetle of See also:South See also:America, Entimus imperialis, is another singularly beautiful weevil; its See also:colour is See also:black, studded with spangles of See also:golden See also:green. The immense See also:family of the Curculionidae includes members which differ greatly from one another in See also:size, colour, and appearance; even the rostrum, the most striking See also:common characteristic, varies greatly. The form of the body is very various: some are rounded or See also:oval, others elongated, almost linear; some are covered with warty protuberances, whilst others are smooth and shining, often with a metallic lustre. One of the commonest members of this family in Great Britain is the See also:nut weevil, Balaninus nucum. It is of a brownish colour, varied with yellow, the legs reddish. Its rostrum is unusually See also:long, being five-sixths of the body length in the See also:female, and slightly shorter in the male. The antennae are 7-jointed. The first three See also:joints are much longer than thick; the four fc,llowing are shorter, and the seventh not longer than thick.

The larva is very common in See also:

hazel nuts and filberts. When the nuts are about half-grown, the female bores, with its rostrum, a See also:minute hole in the still comparatively soft nut-See also:shell, and deposits an See also:egg within the nut. The egg is said to be pushed in by means of the long rostrum. As the nut grows the slight puncture becomes almost obliterated, so that it is unnoticed by all but the most observant See also:eye. The larva is a thick white See also:grub with a brownish head, bearing fleshy tubercles along its side. It feeds upon the substance of the nut. The nuts which are infested by this See also:insect are usually the first to fall to the ground; the larva then bores a round hole through the nut shell, by means of its jaws, and creeps out. It hides itself in the ground during the See also:winter, and in the See also:spring it passes into the pupa See also:stage, from which it emerges about See also:August as the full-grown insect. A nearly allied form, Balaninus glandium, attacks both hazel nuts and acorns. In an unobtrusive way weevils do immense harm to vegetation. This is effected not so much by their See also:numbers and their See also:powers of See also:consumption, as amongst caterpillars, but by their habits of attacking the essential parts of a plant, and causing by their injuries the See also:death of the plant affected. They destroy the See also:young buds, shoots and fruits, and attack the young See also:plants in their most delicate See also:organs.

Many of them devour See also:

seed, as the See also:corn weevils, Calandra granaria and C. eryzae, and in this way vegetation is severely injured, and its spread seriously checked. Others cause much damage in forests, by See also:boring under the bark and through the See also:wood of trees, whilst some even burrow in the See also:tissue of the leaves. The Brenthidae, Anthribidae and Scolytidae are described in the See also:article COLEOPTERA. The Bruchidae are often called " weevils," but they have no See also:close See also:affinity with the Rhynchophora, being nearly allied to the Chrysomelidae or See also:leaf beetles. The antennae are straight, and inserted upon the head just in front of the eyes; they are 11-jointed, and serrated or toothed in the inside. Bruchus pisi causes considerable damage to See also:pease; during the spring the beetle See also:lays its eggs in the young See also:pea, which is devoured by the larva which hatches out in it. (A. E. S.; G. H.

End of Article: WEEVIL

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