Part 36
The _Hydrophili_, very different to the group which we shall presently consider, are herbivorous, and are to be found on the leaves of aquatic plants. The _Hydrophilus piceus_ (Fig. 471), which attains to an inch in length, is common in our fresh waters. It must not be seized without taking precautions, as its breast is provided with a strong point, which pierces the skin. It draws in air by thrusting its antennæ out of the water, and placing them against its body, the bubbles of the air, which get involved in a sort of furrow, slip under the body, and fix themselves to the hair, in such a manner that the animal seems to be clothed in pearls. It is thus the air reaches the spiracles. The female of the _Hydrophilus_ is sometimes seen clinging to aquatic plants, head downwards, forming her cocoon, terminated by a long pedicle, in which she places her eggs, by means of the two bristles situated at the extremity of the abdomen (Fig. 472). After having drawn this after her for some time, she leaves it to itself in calm water. At the end of a fortnight there come out from it little brown larvæ, very active, which ascend the water plants. These larvæ are at the same time herbivorous and carnivorous. They live on plants and small molluscs, which they seize from underneath, and whose shell they break by pressing them against their back, to extract from it the animal. If attacked, they emit a black liquid, which discolours the water, and enables them to escape. At the end of two months the larva comes out of the water, and burrows into the ground to undergo its metamorphosis into a pupa (Fig. 473), which becomes a perfect insect a month afterwards. The latter gets its colour little by little, and comes out of the ground at the end of twelve days. According to M. Dumeril, the intestine of the larva grows gradually longer and longer, and its diet becomes that of herbs, the adult preferring vegetable food to animal matter. It is at the end of summer that the _Hydrophilus piceus_ becomes perfect, and it passes the winter in a state of torpor at the bottom of the water. The females lay in the month of April. A small species, _Hydrous caraboides_, is commoner than the large one; its body is more rounded behind.
We are now going to consider a series of aquatic and carnivorous insects; the _Dytisci_, Water Beetles, the _Cybisters_, and the _Gyrinidæ_, or Whirligig Beetles. These are perfect corsairs, whose rapacity even exceeds that of many of the land Coleoptera. Not contented with devouring one another, when pressed by hunger, with attacking especially the larvæ of all aquatic insects, such as the _Libellulæ_ and _Ephemeræ_, they feed also on molluscs, on tadpoles, and on small fish. It is easy to rear them in captivity. If confined in a small aquarium, their habits would be much more amusing than a few golden fish, which one meets with everywhere, and which are only good enough to amuse European _Schaabahams_. Care must be taken to cover the aquarium at the top with gauze, to prevent the perfect insects from escaping. This tribe is not very numerous nor varied in its forms. An oval body, legs curved and widened into oars, provided with hairs, distinguish the insects which compose it. They imbibe air at the surface of the water.
The most carnivorous of this group are the _Dytisci_ and the _Cybisters_. They may be called the sharks of the insect world. Nothing which lives in the water is safe against the voracity of the _Dytiscus_. They attack small molluscs, young fish, tadpoles, larvæ of insects, and suck greedily the bits of raw meat which are thrown to them. They may be kept in an aquarium for many years by feeding them on animal matter. Their oval-shaped body, with its sharp sides, permits them to cut through the water with great ease--the hind legs serving as oars. They are to be found in stagnant waters during the greatest part of the year, but principally in autumn. During the winter they bury themselves in the mud and under moss. The females lay their eggs in the water. The larvæ are long, swelling out at the middle, furnished with hairs, and grow rapidly. To undergo their metamorphosis into pupæ they bury themselves in the earth.
The perfect insects are amphibious, and fly from one pond to another to satisfy their voracious appetites. The most common species of this genus is the _Dytiscus marginalis_ (Fig. 474), of a dark greenish brown, yellowish on the sides. The elytra of the male are smooth; those of the female are fluted. The front leg of the male is provided with suckers. The larva is brown; the pupa of a dirty white.
The _Dytiscus marginalis_ sometimes attacks _Hydrophilus piceus_. It pierces it between the head and the thorax, that is, in the weak point of the cuirass, and devours it, in spite of its being the stronger. The largest of the _Dytisci_, the _Dytiscus latissimus_ (Fig. 476), is almost confined to the north of Europe. The _Cybisters_ abound especially in warm countries. The _Cybister Roeselii_ (Fig. 477), a European species, has the reputation of having been taken in England. This group contains also a great number of insects more or less resembling the preceding in their conformation and habits. We will confine ourselves to representing a few by figures.
The _Gyrinidæ_, which come very near to the _Dytiscidæ_, like water which is clear and a little agitated. They are small black insects, living in troops, and which swim with rapidity, describing incessantly capricious circles, which has gained for them the name of "Whirligigs." They are remarkable for the disposition of their eyes, which are double; so that the _Gyrinidæ_ seem to have four eyes. The lower ones look into the water and watch for the prey or the fish that advances as an enemy; whilst the upper eyes look upwards towards the air, and warn the insect of the approach of enemies from above. To escape from fish, the _Gyrinus_ jumps out of the water, and also makes use of its wings; to escape from birds it dives rapidly. This activity, and this double sight, make the capture of the _Gyrini_ a task of great difficulty. They must be caught with a net. At the moment of being seized they emit a milky and foetid liquid.
The females lay their eggs end to end, on the leaves of aquatic plants. The larvæ are long and narrow, and of a dirty white. They come out of the water at the end of the summer, and form for themselves a cocoon on the plants bordering the banks. After a month, the perfect insect is hatched, and plunges into the water. The _Gyrinus striatus_ (Fig. 496) is found in the waters of southern Europe.
All these species are of small size, and do not exceed a fifth of an inch in length; but in the tropics we find _Gyrini_ two-thirds of an inch long. One of these species, _distinctus_, exists in the little lake of Solazies, in Réunion Island, noted for its mineral waters. The visitors amuse themselves by fishing for this insect with a line baited with a bit of red cloth, which it attacks. It is found also in a mineral spring in Algeria. The _Epinecti_ (Fig. 498) are large _Gyrinidæ_ from Brazil, with very long front legs.
The carnivorous land insects _par excellence_--those which are most formidable, on account of their ravages and voracity--are the _Carabidæ_. This family, one of the most numerous of the Order Coleoptera, consists of insects with long legs, and armed with powerful mandibles, suited for tearing their victims to pieces. They are the lions and the tigers of the Coleoptera, whilst the _Necrophori_ and the _Silphæ_ play the part of hyænas and jackals. The eyes of the _Carabidæ_ are very prominent, which allows them to see their prey at a great distance. They take refuge under stones and under the bark of trees; but in fine weather they are also to be seen running along roads. Ardent and audacious, it is by no means rare to see them attacking species much bigger than themselves. The activity which distinguishes these insects is found also in their larvæ, which pursue living prey, instead of remaining shrouded in the midst of their food, like the larvæ of the _Scarabæidæ_.
These carnivorous insects are very numerous--a fortunate circumstance, considering the immense quantity of small noxious creatures, caterpillars, weevils, and an infinity of other parasites, the pests of agriculture, which they destroy. The popular prejudice, then, is to be regretted, which leads ignorant farmers to exterminate them. They ought, on the contrary, to be introduced into market gardens, as toads are, and as cats are into granaries. "The _Carabidæ_," says M. Michelet, "immense tribes of warriors, armed to the teeth, which, under their heavy cuirasses, have a wonderful activity, are perfect rural constabulary, day and night, without holidays or repose, protecting our fields. They never touch the smallest thing. They are occupied entirely in arresting thieves, and they desire no salary but the body of the thief himself." But ignorance destroys these useful hunters. Children, seduced by the richness of the elytra of the _Carabi_, amuse themselves in catching these vigilant protectors of our farms, without knowing the bad effect of what they are doing. Fortunately, education is spreading little by little in the country; the farmers begin to be awakened to their true interests, and to know how to distinguish the useful animals which it behoves them to preserve in their fields for the safeguard of their crops. In some places in France they have already made attempts to introduce the _Carabidæ_ and the _Cicindelidæ_ into gardens, and they have found them succeed very well.
The true _Carabi_ are to be known by their oval convex body, their long antennæ, and elegantly-carved thorax. They are, in general, of more massive forms than the _Cicindelidæ_, which compose a kindred family. The latter form, in some sort, the vanguard and the light troops; the others, the heavy battalions. The _Carabi_ coming out in general at night, or at least at twilight, and keeping themselves hidden under stones during the day, it is not easy to observe their manoeuvres.
The _Carabus auratus_ (Fig. 499), which abounds in fields and gardens on the Continent, may be considered as the type of this genus. It has elytra of a beautiful green, with three ribs, and the legs yellowish. When it is touched it disgorges a black and acrid saliva, and ejects from the abdomen a corrosive liquid of a disagreeable odour. It lives on the larvæ of other insects. It has been seen to attack even large insects, such as the cockchafer.
In England and the environs of Paris, _Carabus violaceus_ (Fig. 500), whose dress, of a sombre colour, is surrounded by shades of red and violet, is met with. In the Pyrenees many _Carabi_ with metallic reflections are found, whose beautiful colours are the delight of collectors; the _Carabus splendens_, the _Carabus rutilans_, &c. But the most beautiful insects of this tribe come from Siberia and the north of China. Let us mention, for example, the _Carabus smaragdinus_, of a beautiful grass-green; the _Carabus Vietinghovii_, of a beautiful blue black, bordered with azure, with a golden band, &c.
The _Carabus Adonis_ (Fig. 502) is not rare in Alsace, and is found on the banks of streams.
The long flat larvæ of the _Carabi_ live in the trunks of trees, among leaves, under moss, &c. They are active, and live on other insects. Fig. 504 represents the larva of the _Carabus auronitens_.
Another genus of the same family is _Calosoma_. They have wings under their elytra--the true _Carabi_ have not--which they use in passing from one tree to another.
In the month of June is to be found on oak trees the beautiful _Calosoma sycophanta_ (Fig. 508), the occasional occurrence of which in England is unquestionable; it is, however, presumed that the specimens have reached our shores from the Continent by flight, favoured by strong easterly winds. This insect is of a beautiful violet blue, having the antennæ and the legs black, and the elytra of a splendid golden green, with longitudinal streaks. According to Réaumur, the larva of the _Calosoma_ often chooses a home in the nest of the Procession-Moth Caterpillar (_Bombyx processionea_), on oak trees, and it very soon rids the tree which is infested by them.
The _Calosoma auropunctata_ is found in the south of France. Its larva (Fig. 507) devours snails, and establishes itself in their shells. These larvæ have been known to fill themselves so full of food as to become double their natural size, in which state they are sometimes devoured by those of their own species. A smaller kind, the _Calosoma inquisitor_, is very frequently to be met with in woods. Fig. 508 presents _Calosoma sycophanta_ pursuing a Bombardier (_Brachinus explodens_), which squirts out a vapour of pungent odour.
In the countries of the south-east of Europe, and in Asia Minor, one finds enormous _Carabidæ_, the _Procrustes_ and the _Proceri_, which attain nearly two inches in length, and whose integuments resemble very rough shagreen. One species alone is met with in France, the _Procrustes coriaceus_ (Fig. 509). In Austria is found the _Procerus gigas_ (Fig. 510).
The genus _Omophron_ (Fig. 511) contains small, almost globular _Carabidæ_ of a pale yellow, with green lines, and which live in the sand bordering rivers. The _Nebrias_ in general prefer mountainous countries. The largest species, the _Nebria arenaria_ (Fig. 512), is found all along the coast of the Mediterranean, and even on the western shores of France. But its colours grow paler as it advances northward on the African coast. It is of a bright yellow with black lines. The _Nebrias_ hide themselves either under masses of seaweed cast up by the waves, or under the stumps of trees cast ashore by the sea. When they are deprived of their place of shelter, they run away with such rapidity that it is very difficult to catch them. In Senegal is found the genus _Tefflus_ (Fig. 513), great black _Carabidæ_ with fluted elytra.
Other kindred genera are--_Damaster_ (Fig. 514), remarkable for elongated pointed elytra; _Anthia_ (Fig. 515), which is met with in sand in Africa and in India, and whose head is armed in a formidable manner; and _Campylocnemis_, of which _Schroeteri_ (Fig. 516), an Australian insect, of a bright black, attains to more than an inch and three quarters in length, and whose short serrated legs enable it to hollow out the ground. There is found on the coasts of the south of France a representative of this group in the _Scarites lævigatus_ (Fig. 517), which conceals itself in a hollow, like the cricket, and devours everything which comes within its reach.
The innumerable tribe of _Harpalidæ_ contains carnivorous beetles of very small size, sometimes of a bronze-green, sometimes black, either dull or shining, and which render great service to our gardens. Hidden under stones, in dry leaves, at the foot of trees, they attack a number of small insects, caterpillars, millepedes, &c., and thus exterminate a quantity of vermin. The _Harpalus æneus_ (Fig. 518), which is seen shining in the midst of the paving stones like a little bronze plate, is found everywhere. The _Galeritas_ (Figs. 519 and 520) are distinguished by their antennæ, which are thick at the base; they exhale a very strong odour: nearly all are peculiar to America. One of the most curious insects of this tribe is the _Mormolyce phyllodes_ of Java (Fig. 521) whose elytra project in such a manner as to give it the appearance of a leaf. It lives under bark. The larva and the pupa (Fig. 522) resemble those of other genera of which we have been speaking.
The next great family of the tribe of carnivorous beetles is composed of the _Cicindelidæ_--slender insects, with large prominent heads, very long legs, and which are very active in their movements. The _Cicindelidæ_ like sandy plains. When the sun shines they fly in a zig-zag manner, but their flight is not continued for long together. In dull weather they are to be seen running on the turf or hiding themselves in holes, and are met with on the sea-shore, where they are seen sometimes to pop up by hundreds. They live on flies and little shrimps, which abound on the sea-shore.
The _Cicindela campestris_ (Fig. 523), or Tiger Beetle, is of a beautiful green, spotted with white; the abdomen is of a bronze red. In this country it is the commonest of the genus. The _Cicindela hybrida_, of a dull green, relieved by light bands, inhabits sandy woods. The _Cicindela maritima_ differs from the preceding. The _Cicindela sylvatica_, which flies very well, is not easy to catch, and is to be often met with in the warm glades of the forest of Fontainebleau and at Montmorency; it is not unfrequent here. Its colour is brown, spotted with white; it diffuses a strong smell of the rose, to which succeeds, on being seized, the acrid odour of the secretion which it disgorges. We here represent the _Cicindela Dumoulinii_ (Fig. 524), the _Cicindela rugosa_ (Fig. 525), the _Cicindela scalaris_ (Fig. 526), the _Cicindela heros_ (Fig. 527), the _Cicindela quadrilineata_ (Fig. 528), and the _Cicindela capensis_ (Fig. 529).
The ferocity of these insects is remarkable. They quickly tear off the wings and legs of their victim, and suck out the contents of its abdomen. Often, when they are disturbed in this agreeable occupation, not wishing to leave it, they fly away with their prey; their flight, however, is not sufficiently powerful to allow of their carrying to any great distance such a heavy burden. When a _Cicindela_ is seized between the fingers, it moves about its mandibles and endeavours to pinch, but its bite is inoffensive and not very painful. They are prodigiously active in running. Armed with jaws which are powerful enough to overcome their victims and to seize them at once, they can dispense with stratagem.
Their larvæ (Fig. 530) are soft, and have short legs. To satisfy their voracity they are obliged to lie in ambush in holes. They are two-thirds of an inch long; their head is horny and in the form of a trapezium. The first segment is also horny, and of a metallic green. The eighth has a pair of tubercles with hooks, of which the larva makes use in ascending and descending its vertical hole, like a sweep in a chimney. This hole (Fig. 531) is a foot or more deep. To dig it, the larva employs its mandibles and its legs in the following manner: it twists itself round, loads with earth the flat surface which covers its head, climbs along the chimney by twisting itself into the form of the letter Z, and thus transports its load, as a bricklayer's labourer carries a hod of mortar up a ladder. Arrived at the mouth of the hole, it throws to a distance the rubbish with which its head is loaded; or, if too heavy, it simply deposits it, pushing it away as far as possible. It is difficult to watch their proceedings, for they are very mistrustful, and retire immediately into their hole when alarmed. They remain in ambush at the entrances of these subterranean passages, which they hermetically seal with their head and thorax. It is a species of pitfall which sets itself in motion the moment anything endeavours to pass it. The unfortunate who ventures is precipitated into the well, and the _Cicindela_ forthwith devours it. These habits remind one of those of the ant-lion. When the time arrives for the metamorphosis, the larva of the _Cicindela_ enlarges the bottom of its hole, and stops up the entrance with earth before changing. The pupa (Figs. 532, 533) is of a pale glossy yellow, covered with small spines. The metamorphosis takes place between August and October; the perfect insect emerges in spring.
Nearly akin to the _Cicindelas_ are the _Tetrachas_ (Figs. 534, 535, 536), from Africa and tropical America; the _Manticoras_ (Fig. 537), which are distinguished by their robust and thick-set appearance; the _Pogonostomas_ (Fig. 538), which live in Madagascar; the _Ctenostomas_, peculiar to America (Fig. 539), remarkable for the length of their pendent and bristly palpi; the _Omus_, of California; the _Therates_ (Fig. 540), insects of the East Indian Islands, &c.