Page:Encyclopædia Britannica, Ninth Edition, v. 6.djvu/153

COLEOPTERA 129 and this resemblance has given rise to the supposition that at some distant period a land connection existed between the two continents ; it is more probable, however, as Wallace holds, " that it may have arisen from intercom munication during the warm southern period when floating timber would occasionally transmit a few larvae from island to island across the Antarctic seas." The Neotropical Region comprehends southern and Central America and the West Indies, and is enormously rich in Longicorn Beetles, having no fewer than 516 genera, of which 487 are found nowhere else. The most remarkable fact in the distribution of the Stag Beetles (Lucanidae) is their almost total absence from the tropical parts of this region, and their presence in North America, while in the old world they are specially characteristic of the hottest parts of the Oriental and Australian Regions. The Nearctic Region comprises the northern and temperate parts of America, and is comparatively poor in Coleoptera, showing greater affinity, however, with the Pahearctic than with the con tiguous Neotropical Region. The insects belonging to this extensive Order comprise numerous well-defined and generally recognized families, but great diversity of opinion exists as to the best mode of grouping these together so as to exhibit their natural affinities. Geoffrey, a French naturalist, was the first to make use of the number of joints in the tarsi for this purpose, a method adopted and extended by Olivier, and brought into general use by Latreille. According to the tarsal system the Coleoptera are divided into the following four sections : (1) PENTAMERA, in which all the tarsi are five-jointed ; (2) HETEROMERA, with five articulations to the first four tarsi and four to the posterior pair ; (3) TETRAMERA, with four articulations to all the tarsi ; and (4) TRIMERA, with all the tarsi three-jointed. Macleay, an English naturalist, altogether rejected the tarsal system of Geoffrey, and founded his .five primary divisions on characters derived from the larvae of those insects a system adopted by Stephens in his Classification of British Insects, and by several other English writers on this subject. The tarsal system is to a large extent artificial, and when slavishly followed brings together forms which in other respects differ very widely, while separating many that are as obviously related. Its simplicity and consequent easiness of application have, in the absence of a more natural system, led to its very general adoption by both British and foreign naturalists, who do not, however, apply it where obviously unnatural. PENTAMERA. The majority of the beetles in this section have the tarsi of the feet five-jointed, and they comprise fully one-half of all the known species of Coleoptera. It is subdivided into the following 8 groups : I. Geodtphaga, or Predaceous Land Beetles, resemble the succeeding group and differ from other Coleoptera in having the outer lobe of the maxilla? distinct and articulated, thus appearing to possess six palpi. They are extremely active, their legs being admirably adapted for running; the majority are nocturnal in their habits, secreting themselves under stones and clods of earth ; and all are carnivorous, feeding on other insects and occasionally devouring individuals of their own species, while their larvae are equally predaceous. They are exceedingly numerous in temperate regions, and are eminently serviceable in checking the increase of insects which feed on fruit and grain. The mandibles, by which they seize and tear their living prey, are long horny organs, hooked and sharp at the [joints, and toothed on the inner edges. This group includes the Tiger Beetles, Cidndelidce ( Plate VI. figs. 4, 9-1 2), so called from the fierceness of their disposition, and probably also from the spots and stripes with which the elytra are generally adorned. Most of the species are diurnal, frequenting hot sandy districts, enjoying the bright sunshine, and flying for short distances with great velocity. They are elegant in form and adorned with brilliant metallic colours, the prevalent hue being a golden green. The habits of the larvae of these insects are very remarkable. Unfit, from the softness of their bodies and the slowness of their motions, effectually to protect them selves from the attacks of their enemies, or to capture their prey on the surface of the ground, the larvae of the Tiger Beetles have recourse to stratagem in order to effect these purposes. By means of their short thick legs, assisted by their powerful sickle-shaped jaws, they dig burrows in the sandy banks which they frequent, vertical for some distance, and afterwards curving so as to become horizontal. Thete are about a foot in depth, and within them the Tiger Beetle remains during its larval and pupa stages. In seeking its food the creature makes its way from the bottom of its den until the head segment, which is broad and flat, reaches the level of the ground, and thus blocks up the aperture of its tunnel. It remains fixed in this position by means of two bent hooks placed on the upper surface of the "eighth segment, which is considerably thicker than the others, until an unsuspecting ant or other insect passing over or close to it is seized by ite formidable jaws and speedily conveyed to the bottom of the pit-fall, where it is greedily devoured. Should the tunnels of different individuals happen to come in contact, the more powerful larva is eaid to devour its weaker neighbour. When full grown it closes the mouth of its burrow and there undergoes metamorphosis. The best known and most beautiful of British species is the Tiger Beetle, Cicindela campestris, of a sea-green colour with six whitish spots on the elytra. When handled it exhales, according to Westwood, a pleasant odour like that of roses. Ground beetles (Carabidce) are generally less brilliant in colour than the Tiger forms, being more nocturnal in their habits, and with the jaws less formidably toothed. Many of the species are entirely apterous, with the elytra more or less soldered together, and the majority of them secrete an acrid juice which they expel when menaced or attacked. Of the latter the most remarkable are the Bombardier Beetles, Brachinus (Plate VI. fig. 8). These congregate together under stones, and when disturbed discharge a caustic fluid of an extremely penetrating odour, and so volatile that no sooner does it come in contact with the atmosphere than it passes into a vapour, accompanied by a considerable explosion, during which they seek to escape. When placed on the tongue this fluid causes a sharp pain and leaves a yellow spot somewhat similar to that produced by a drop of nitric acid. The Bombardiers are said to be capable of giving off as many as 1 8 of such discharges at a time. One of the most beautiful of European beetles is the Calosoma sycophanta (Plate VII. fig. 2), belonging to this group. Its body is of a deep violet colour, and the elytra, which are striated and punctured, are of a rich green and gold tint. Both in the larva and perfect states these beetles frequent the trunks and branches of the oak, where they find their favourite food the large caterpillars of the Procession ary Moth (Bombyx processioned), of which they devour enormous numbers, apparently undeterred by the hairs which clothe the body of the caterpillar, and which when seized by the human hand cause considerable pain. One of the most curious of Carabideous Beetles, Mormolyce 2 Jtyllodcs ( Plate VI. fig. 5), is a native of Java. Its body is about 3 inches long and 1 inches across the elytra. The latter are flat, thin, and greatly dilated, while the other parts of the body are remarkably depressed, the beetle thus somewhat resembling the Orthopterous leaf-insects, and hence the specific name phyllodes, or leaf-like. Many of the ground beetles, such as the typical Carali (Plate VI. figs. 6, 7) and the Calosoma, live in the sunshine and are generally brilliant in colouring ; others spend their existence

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