The most interesting division of the Coprides is the group Scarabaeini. No member of this group inhabits the British islands, but in Southern Europe, and in still warmer lands, these Insects are well known from the curious habit many of the species have of rolling about balls of dung and earth. The long hind legs are chiefly used for this purpose, and it is on the peculiar structure of these limbs that the group has been established. Many of the stone Scarabaei found in Egyptian tombs represent some kind of Scarabaeini, and it has been said that the ancient Egyptians looked on these Insects as sacred because of their movements. These must certainly appear very strange to those who see them and are unacquainted with their object. It is stated that the dwellers in the valley of the Nile thought the actions of these Insects, when rolling their balls, were typical of the planetary and lunar revolutions; and that the sudden appearance of the beetles after a period of complete absence was emblematic of a future life. Many accounts have been given of the habits of members of this group, but according to Fabre all are more or less erroneous; and he has described the habits and life-history of Scarabaeus sacer (Fig. 89), as observed by him in Southern France. These Insects act the part of scavengers by breaking up and burying the droppings of cattle and other animals. The female Scarabaeus detaches a portion of the dung and forms it into a ball, sometimes as large as the fist; this it rolls along by means of its hind legs, by pushing when necessary with its broad head, or by walking backwards and dragging the ball with its front legs. The strength and patience displayed by the creature in the execution of this task are admirable. Frequently the owner of this small spherical property is joined, so Fabre informs us, by a friend, who is usually of the same sex and assists her in pushing along the ball till a suitable place is reached. When this is attained, the owner commences to excavate a chamber for the reception of the ball; sometimes the false friend takes advantage of the opportunity thus offered and carries off the ball for her own use. Should no disappointment of this sort occur, the Scarabaeus accomplishes the burying of the ball in its subterranean chamber, and accompanies it for the purpose of devouring it; the feast is continued without intermission till the food is entirely exhausted, when the Scarabaeus seeks a fresh store of provender to be treated in a similar manner. According to M. Fabre's account these events occur in the spring of the year, and when the hot weather sets in the Scarabaeus passes through a period of quiescence, emerging again in the autumn to recommence its labours, which are now, however, directed immediately to the continuance of the species; a larger subterranean chamber is formed, and to this retreat the beetle carries dung till it has accumulated a mass of the size of a moderate apple; this material is carefully arranged, previous to the laying of the egg, in such a manner that the grub to be hatched from the egg shall find the softest and most nutritive portions close to it, while the coarser and more innutritious parts are arranged so as to be reached by the grub only after it has acquired some strength; lastly, a still more delicate and nutritive paste is prepared by the mother beetle for a first meal for the newly-hatched grub, by some of the food being submitted to a partial digestion in her organs; finally, the egg is deposited in the selected spot, and the chamber closed. Certain of the Coprides exhibit, according to Fabre, some extremely exceptional features in their life-histories. The mother, instead of dying after oviposition, survives, and sees the growth of her young to the perfect state, and then produces another generation. No similar case can be pointed out in Insects, except in the Social kinds; but from these the Coprides observed by Fabre differ profoundly, inasmuch as the number of eggs produced by the mother is extremely small; Copris hispanus, for instance, producing in each of its acts of oviposition only one, two, or three eggs.
Fig. 89—Scarabaeus sacer. Portugal.
ii. The Melolonthides are probably almost as numerous as the Coprides, some 4000 species being already known. The larvae are believed to feed chiefly on roots. Melolontha vulgaris, the common cockchafer, is very abundant in some parts of Europe, and owing to this and to the great damage it causes, has attracted much attention. The memoir by Straus-Durckheim[[82]] on its anatomy is one of the classical works of Entomology. This Insect is so injurious in some parts of France that money is paid by the local authorities for its destruction. M. Reiset informs us that under this arrangement 867,173,000 perfect cockchafers, and 647,000,000 larvae were destroyed in the Seine-inférieure in the four years from the middle of 1866 to 1870. Unlike the Coprides, the larval life in Melolonthides is prolonged, and that of the imago is of brief duration. In Central Europe the life-cycle of the individual in M. vulgaris occupies three years, though in dry periods it may be extended to four years. In Scandinavia the time occupied by the development appears to be usually five years. The fertile female enters the ground and deposits its eggs in two or three successive batches of about fifteen each. The eggs swell as the development of the embryo progresses; the larva emerges about five weeks after the eggs have been deposited, and is of relatively large size. When young the larvae can straighten themselves out and crawl, but when older they lose this power, and when above ground rest helplessly on their sides. In the winter they descend deeply into the earth to protect themselves from frost. The pupa state lasts only a few days, but after the final transformation the perfect Insect may remain motionless for as much as eight months underground before commencing its active life in the air.[[83]] In the perfect state the Insect is sometimes injurious from the large quantity of foliage it destroys. Schiödte[[84]] considered that these larvae (and those of numerous other Scarabaeidae) stridulate by rubbing certain projections on the stipes of the maxilla against the under-surface of the mandible. These surfaces appear, however, but little adapted for the purpose of producing sound.
iii. The Rutelides number about 1500 species; there are many Insects of brilliant metallic colours amongst them, but very little is known as to their life-histories. The larvae are very much like those of Melolonthides.
iv. The Dynastides are the smallest division in number of species, there being scarcely 1000 known; but amongst them we find in the genera Dynastes and Megasoma some of the largest of existing Insects. The horns and projections on the heads and prothoraces of some of the males of these Insects are truly extraordinary, and it does not appear possible to explain their existence by any use they are to their possessors. These structures are but little used for fighting. Baron von Hügel informs the writer that in Java he has observed large numbers of Xylotrupes gideon; he noticed that the males sometimes carry the females by the aid of their horns; but this must be an exceptional case, for the shape of these instruments, in the majority of Dynastides, would not allow of their being put to this use. The development of these horns varies greatly in most of the species, but he did not find that the females exhibited any preference for the highly armed males. The fact that the males are very much larger than the females, and that the armature is usually confined to them, suggests, however, that some sexual reason exists for these remarkable projections. Many Dynastides possess organs of stridulation, consisting of lines of sculpture placed so as to form one or two bands on the middle of the propygidium, and brought into play by being rubbed by the extremities of the wing-cases. This apparatus is of a less perfect nature than the structures for the same purpose found in numerous other beetles. We have no member of this sub-family in Britain, and there are scarcely a dozen in all Europe. Decaying vegetable matter is believed to be the nutriment of Dynastides. The European Oryctes nasicornis is sometimes found in numbers in spent tan. The growth and development of the individual is believed to be but slow.
v. The Cetoniides are renowned for the beauty of their colours and the elegance of their forms; hence they are a favourite group, and about 1600 species have been catalogued. They are specially fond of warm regions, but it is a peculiarity of the sub-family that a large majority of the species are found in the Old World; South America is inexplicably poor in these Insects, notwithstanding its extensive forests. In this sub-family the mode of flight is peculiar; the elytra do not extend down the sides of the body, so that, if they are elevated a little, the wings can be protruded. This is the mode of flight adopted by most Cetoniides, but the members of the group Trichiini fly in the usual manner. In Britain we have only four kinds of Cetoniides; they are called Rose-chafers. The larvae of C. floricola and some other species live in ants' nests made of vegetable refuse, and it is said that they eat the ants' progeny. Two North American species of Euphoria have similar habits. The group Cremastochilini includes numerous peculiar Insects that apparently have still closer relations with ants. Most of them are very aberrant as well as rare forms, and it has been several times observed in North America that species of Cremastochilus not only live in the nests of the ants, but are forcibly detained therein by the owners, who clearly derive some kind of satisfaction from the companionship of the beetles. The species of the genus Lomaptera stridulate in a peculiar manner, by rubbing the edges of the hind femora over a striate area on the ventral segments.
Series II. Adephaga or Caraboidea.
All the tarsi five-jointed; antennae filiform, or nearly so; mouth-parts highly developed, the outer lobe of the maxilla nearly always divided into a two-jointed palpus; supports of the labial palpi developed as joints of the palpi, and in some cases approximate at their bases. Abdomen with the exposed segments one more in number at the sides than along the middle, the number being usually five along the middle, six at each side.
This extensive series includes the tiger-beetles, ground-beetles, and true water-beetles; it consists of six families, and forms a natural assemblage. It is sometimes called Carnivora or Filicornia. The exceptions to the characters we have mentioned are but few. The supports of the labial palpi are frequently covered by the mentum, and then the palpi appear three-jointed; but when the joint-like palpiger is not covered these palps appear four-jointed. As a rule, approximation of these supports is indicative of high development. In some of the lower forms the trophi remain at a lower stage of development than is usual. This is especially the case with the genus Amphizoa, which forms of itself the family Amphizoidae. The Bombardier-beetles make an exception as regards the abdominal structure, for in some of them no less than eight segments are visible, either along the middle line or at the sides of the venter. In Hydroporides (one of the divisions of Dytiscidae) the front and middle feet have each only four joints. Many naturalists unite the Gyrinidae with the Adephaga, and a few also associate with them the Paussidae and Rhysodidae; but we think it better at present to exclude all these, though we believe that both Paussidae and Rhysodidae will ultimately be assigned to the series. The larvae are usually very active, and have a higher development of the legs than is usual in this Order. Their tarsi possess two claws.