Fam. 4. Cicindelidae (Tiger-beetles).—Clypeus extending laterally in front of the insertion of the antennae. Lower lip with the palpi usually greatly developed, but with the ligula and paraglossae very much reduced, often scarcely to be detected. Maxillae with the outer lobe forming a two-jointed palp,[[85]] the inner lobe elongate, furnished at the tip with a hook-like process, which is usually articulated by a joint with the lobe itself. The tiger-beetles are very active Insects, running with extreme speed, and sometimes flying in a similar manner; they are all predaceous, and amongst the most voracious and fierce of the carnivorous beetles, so that they well deserve their name. Bates, speaking of the Amazonian Megacephala, says "their powers of running exceed anything I have ever observed in this style of Insect locomotion; they run in a serpentine course over the smooth sand, and when closely pursued by the hand they are apt to turn suddenly back and thus baffle the most practised hand and eye." He further says that the species he observed (being of diverse colours) agreed in colour with the general colours of the "locale they inhabit." The larvae of Cicindelidae live in deep burrows, sinking more or less vertically into the ground, and in these they take up a peculiar position, for which their shape is specially adapted; the head and prothorax are broad, the rest of the body slender, the fifth segment of the abdomen is furnished on the back with a pair of strong hooks; the ocelli on the sides of the head are very perfect. Supporting itself at the top of the burrow by means of these hooks and of its terminal tube, the larva blocks the mouth of the burrow with its large head and prothorax, and in this position waits for its prey. This consists of Insects that may alight on the spot or run over it. When an Insect ventures within reach, the head of the larva is thrown back with a rapid jerk, the prey is seized by the long sharp mandibles, dragged to the bottom of the burrow and devoured. The burrows are often more than a foot deep, and are said to be excavated by the larva itself, which carries up the earth on the shovel-like upper surface of its head. The female tiger-beetle is endowed with powerful and elongate excavating instruments at the termination of the body, and it is probable that when placing the egg in the earth she facilitates the future operations of the larva by forming the outlines of the burrow. Extremely few larvae of Cicindelidae are known, but they all exhibit the type of structure mentioned above, and apparently have similar habits. Our little British Cicindela, most of which are so active on the wing, agree in these respects with the African species of Manticora, which are entirely apterous, and are the largest of the Cicindelidae. Péringuey found a breeding-ground of M. tuberculata near Kimberley; the larvae were living in the usual Cicindelid manner; but the ground was so hard that he was not able to investigate the burrows, and there were but few Insects that could serve as food in the neighbourhood.
Fig. 90—Cicindela hybrida. Britain. A, larva (after Schiödte); B, imago, male.
The Cicindelidae, although one of the smaller families of Coleoptera, now number about 1400 species; of these about one-half belong to the great genus Cicindela, to which our four British representatives of the Cicindelidae are all assigned. There is no general work of much consequence on this important family, and its classification is not thoroughly established.[[86]]
Fig. 91—Mouth-parts of tiger-beetles. A, Profile of Pogonostoma sp. (Madagascar): a, antenna; b, labial palp; c, maxillary palp; d, palpiform lobe of maxilla; e, mandible; f, labrum. B, Section of head of Manticora maxillosa (South Africa): a, front of upper part of head-capsule; b, gula; c, tentorium; d, eye; e, labrum; f, left mandible; g, maxilla; h, maxillary palp; i, labial palp; k, support of this palp; l, labium.
Tiger-beetles display considerable variety of structure, especially as regards the mouth, which exhibits very remarkable developments of the palpi and labrum (Fig. 91). The tiger-beetles, like most other Insects that capture living prey, do not consume their victims entire, but subsist chiefly on the juices they squeeze out of them; the hard and innutritious parts are rejected after the victim has been thoroughly lacerated and squeezed; the mouth forms both trap and press; the palpi spread out in order to facilitate the rapid engulfing of a victim, then close up under it and help to support it in the mouth; while the labrum above closes the cavity in the other direction. The mouth itself is a large cavity communicating very freely with the exterior, but so completely shut off from the following parts of the alimentary canal that it is difficult to find the orifice of communication; the labium being much modified to form the posterior wall. For the capture of the prey, always living but of various kinds, a mechanism with great holding power and capable of rapid action is required. The mouth of the terrestrial Manticora (Fig. 91, B), exhibits great strength; some of the chitinous parts are extremely thick, the mandibles are enormous, the palpi, however, are comparatively low in development. In the arboreal genus Pogonostoma the palpary structures (Fig. 91, A) attain a development scarcely equalled elsewhere in the Insect world. The great majority of the Cicindelidae are inhabitants of the warmer, or of the tropical regions of the world, and very little is known as to their life-histories; they show great diversity in their modes of hunting their prey. Some are wingless; others are active on the wing; and of both of these divisions there are forms that are found only on trees or bushes. Some, it is believed, frequent only the mounds of Termites. The characteristic feature common to all is great activity and excessive wariness. The genus Pogonostoma, to which we have already alluded, is confined to Madagascar, where the species are numerous, but are rare in collections on account of the difficulty of securing them. Raffray informs us that certain species frequent the trunks of trees, up which they run in a spiral manner on the least alarm. The only way he could obtain specimens was by the aid of an assistant; the two approached a tree very quietly from opposite sides, and when near it, made a rush, and joined hands as high up the trunk as they could, so as to embrace the tree, when the Pogonostoma fell to the ground and was captured.
Fig. 92—Leistus spinibarbis. A, Larva (after Schiödte); B, imago. Britain.
Fam. 5. Carabidae (Ground-beetles).—Clypeus not extending laterally in front of the antennae. Maxillae with the outer lobe destitute of an articulated hook at the tip. Antennae covered (except the basal joints) with a minute pubescence. Hind legs not very different from the middle pair, formed for running, as usual in beetles. This is one of the largest and most important of the families of Coleoptera, including as it does 12,000 or 13,000 described species. In this country Carabidae are nearly entirely terrestrial in habits, and are scarcely ever seen on the wing; many of the species indeed have merely rudimentary wings; in the tropics there are, however, many arboreal forms that take wing with more or less alertness. The larvae (Fig. 92, A) are usually elongate in form and run freely; they may be known by their tarsi ending in two claws, by the exserted, sharp, calliper-like mandibles, by the body ending in two processes (sometimes jointed) and a tube of varying length projecting backwards. The pupae usually have the hind pair of legs so arranged that the tips of the tarsi project behind, beyond the extremity of the body. The Carabidae are carnivorous and predaceous both as larvae and perfect Insects; they attack living Insects, worms, or other small, soft creatures, but do not disdain dead specimens. Some species of Carabus, found in North Africa where snails abound, are specially formed for attacking these molluscs, having the head long and slender so that it can be thrust into the shell of the snail. A few species have been detected eating growing corn, and even the young seeds of some Umbelliferae; these belong chiefly to the genera Harpalus, Zabrus, and Amara. Some species of the abundant genera Pterostichus and Harpalus, are said to be fond of ripe strawberries. The most anomalous forms of Carabidae are the Pseudomorphides, a sub-family almost peculiar to Australia, the members of which live under bark, and have but little resemblance to other Carabids owing to their compact forms and continuous outlines. The genus Mormolyce is one of the wonders of the Insect world on account of the extraordinary shape of its members; the sides of the elytra form large crinkled expansions, and the head is unusually elongate. These Insects live on the underside of fallen trees in the Malay Archipelago and Peninsula; no reason whatever can be at present assigned for their remarkable shape.