Page:Encyclopædia Britannica, Ninth Edition, v. 6.djvu/159

Rh COLEOPTERA 133 of Northern Europe, does great damage by boring into the timber of the oak tree. HETEROMERA. The beetles comprising this section have five joints to the first four tarsi, and four to the posterior pair, and form two groups, Trachelia and Atrachelia. I. Trachelia have the head triangular or heart-shaped, and connected with the thorax by a kind of neck or abrupt pedicle. Most of the species in the perfect state live on various plants, of which they devour the foliage or suck the juices, and many when seized bend their heads, contract their limbs, and simulate death. This group includes the Oil Beetles (Meloe) (Plate VIII. fig. 2), large black insects, destitute of wings, and with short elytra. They secrete an oily fluid possessing slightly blistering properties, which when alarmed they emit from the joints of their legs, and when eaten by cattle, as they sometimes are when feeding on the wild buttercups of pasture-lands, they produce sores in the mouth. In some parts of Spain they are used instead of the Blistering Fly, or are mixed with it. The young larvae of several species of Oil Beetles, it has been ascertained, get conveyed to the nests of bees, where alone they can find their appropriate food, and where also they undergo metamorphosis. The most important insect of this group is the Spanish Fly, or Blistering Beetle (Lytta vesicatoria) (Plate VIII. fig. 19), found abundantly in South- Western Europe, but of rare occurrence in England. It is a handsome insect of a golden green colour, and measures about three-fourths of an inch in length. In Spain, where this species is most abundant, they are collected for commercial purposes in the month of June. A sheet is placed beneath the trees frequented by the blister-flies, and the branches are shaken, so as to cause the insects to fall off. They are then killed by exposure to the vapour of vinegar, and completely dried after they are dead. The blistering principle, known to chemists as cantharadin, is contained in their integuments. See CANTHARIDES. II. The Atrachelia have no distinct neck, the part of the head behind the eyes being immersed in the thorax. They are in most cases nocturnal insects, obscure in colour, and slow in motion. The Church-yard Beetle (Blaps mortisaga)) (Plate VIII. fig. 1) is one of the commonest species. It is of a shining black colour, avoids the light, and emits an offensive odour. It is found in cellar*, store-rooms, and the neglected parts of houses, feeding on rubbish of all kinds, and regarded as of evil omen by the superstitious. It is very tenacious of life, having been known to survive several hours immersion in spirits of wine, and cases are on record in which the larvae have been discharged from the human stomach. The Meal-worm is the larva of Tenebrio molitor (Plate VIII. figs. 4, 5), a well-known insect belonging to this group, which appears in the evening in the least frequented parts of houses. It is found abundantly in flour-mills and bake-houses, greatly relishing the heat of the latter. The larvse, which are long, cylindrical, and of an ochry yellow colour, pass their lives enveloped in the flour which forms their favourite food, and in the midst of which they become pupae. While injurious to flour and bran, and destroying great quantities of ship biscuits, the Meal-worm is used as bait by fishermen, and as food for the nightingale and other pet insectivorous birds. TETRAMERA. The beetles composing this section have four apparent joints to all the tarsi, but in most cases the tarsi are in reality five-jointed, the fourth being so minute as to have been overlooked by the founders of the tarsal system. For this reason Westwood proposed the term Pseudo- tetramera in place of Tetramera, a change which has been adopted by several systematic writers. This section in cludes a vast number of small or moderate sized beetles, all vegetable feeders, found in the perfect state on flowers and plants. It is subdivided into the three following groups : I. Rhynchophora, the species of which are readily re cognized by having the front of the head produced into a rostrum or snout, which bears the organs of the mouth at its extremity. The larva? are either entirely destitute of legs, or havfe them in the form of small fleshy tubercles, and are in most cases equally destitute of eyes. The most numerous and best-known tribe of Rhynchophorous beetles are the Weevils (Plate VIII. figs. 8, 9, 15, 16, 20, 22), of which several thousand species have been described, and whose larvae, dwelling in the interior of fruits and seeds, do immense damage to the produce of the farmer, the grain dealer, and the horticulturist. They are generally minute in size and exceedingly varied in colour, the South American forms, known as Diamond Beetles, being among the most gorgeous of insects. These owe their colour, which in the finest of them is a light-green tinged with golden yellow, to the presence of minute scales on the 1 elytra. The Weevil par excellence (Cedandra granaria) measures about one-eighth of an inch in length, is of a pitchy red colour, and does great damage in granaries. The female buries herself among the grains of wheat, in each of which she bores a small hole, where she deposits a single egg, thereafter closing the aperture with a glutinous secretion. The egg is soon hatched, and the larva, furnished with two strong mandibles, eats out the interior of the grain, becomes a nymph, and in the course of eight or ten days is transformed into the perfect insect, ready to raise another brood. The whole time occupied with their reproduction, from the union of the sexes to the appearance of the perfect Weevil, is not more than 50 days, and it has been calculated that from a single pair 2 3, GOO individuals may thus take origin in a single season. Grain injured by these insects is readily detected, from the fact that it floats when immersed in water. Kiln-drying the grain is the mode most generally adopted for arresting the evil. Filberts, acorns, rice, the sugar-cane, and the palm tree have each its own species of Weevil. The Palm Tree Weevil (Calandra palmarttm) is the largest of the tribe, measuring 2 inches in length, and its larvae, as well as those of the sugar-cane species, are, v/hen cooked, considered delicacies by the natives of Guiana and the West Indies. Bruchus pisi (Plate VIII. fig. 12), belonging to another family of this group, deposits its eggs in peas, the interior of which is devoured by the larva. It has probably been introduced into Britain from America, where its ravages are occasionally such as totally to destroy the pea crop over large districts. The larvae of many species burrow beneath the bark of trees and thus destroy immense quantities of timber. Of these the most familiar are Scolytus destructor, whose curiously designed burrows in the bark of the elm are well known, and the Typographic Beetle (Tomicus typograpliicus), so called from the resemblance which its burrows, made in the soft wood immediately beneath the bark, bear to printed characters. II. Longicornes (Plate VIII. fig. 13) form an extensive group of beetles characteristic of tropical forests, and readily distinguished by the great length of their antennae, which in some cases are several times longer than the body. These are usually setaceous or filiform, and are occasionally adorned with tufts of hair at the joints (Plate VIII. fig. 3). The larvae of almost all the Longicorns live in the interior, or beneath the bark, of trees, perforating the timber of the largest forest trees, and thus hastening in these the natural process of decay. They are either apodal, or furnished with inconspicuous feet, but progress chiefly by the aid of small tubercles on the upper and under surfaces of the segments. The female is provided with an ovipositor of horny consistence, issuing from the posterior segment, by means of which the eggs are deposited in cracks and fissures of wood. The larvae remain for several years buried in tho