TERMITES AT WORK.
This shows one of the most destructive of wood-eating insects, nearly of the natural size.
In a state of nature termites are undoubtedly beneficial. They are scavengers, in fact, whose duty it is to remove the dead and decaying wood which would otherwise encumber the ground for many years. But in civilised districts they are extremely mischievous, books, furniture, and all the woodwork of houses being often completely destroyed by them before their presence is even suspected.
The second division of the order also forms two well-marked groups—namely, the Flat-winged Insects, in which the wings are fully spread, horizontally or obliquely, even in repose, and the Hairy-winged Insects, in which those organs can be folded longitudinally, like the joints of a fan.
Of the former group, the Ant-lion of Southern Europe is a familiar example. The perfect insect is seldom seen, owing to its nocturnal habits. In appearance it is not unlike a small and delicately built dragon-fly, with a yellowish head, a black body, and transparent wings marbled with brownish spots. The larva, however, is terrestrial, and lives in a funnel-shaped pitfall which it scoops out in the sand, always working backwards in a spiral direction, and jerking out the sand with its broad head in an almost continuous shower. Having completed the excavation, it buries itself at the bottom with merely the tips of its jaws appearing above the surface, and there waits for ants or other small creatures to fall down the sloping sides, accelerating their descent, if need be, by flinging sand upon them. The size of the pit varies with that of the insect, the fully grown grub digging down to the depth of about 2 inches, while the cavity is about 3 inches in diameter.
The mouth of the ant-lion grub is very curiously constructed, the jaws lying in a groove on the inner margin of the mandibles, or jaws proper; so that while an insect is held prisoner by the latter, the former can be employed in sucking its juices. When the body of the victim has been completely drained, the empty skin is thrown out of the pit by a jerk of the head.
The chrysalis, too, is remarkable for possessing jaws, by means of which it cuts its way out of the cocoon which it made, when a larva, by spinning grains of sand together with silken threads.
In some South European and African insects allied to the ant-lions the hind wings are modified into extremely long and slender shafts, slightly expanded at the extremities. In an Indian species belonging to a related genus these wings are scarcely more than threads, and bear a superficial resemblance to the attenuated limbs of certain gnats. One group, of which a Japanese species is a well-known representative, is characterised by the long, slender, and clubbed antennæ.
Photo by W. Saville-Kent, F.Z.S.] [Milford-on-Sea.