leaves of this plant, from being thick and juicy, giving them space to work and plenty to eat.

Most of the solitary leaf-miners either cannot or will not construct a new mine, if ejected by an experimenter from the old, as we have frequently proved; but this is not the case with the social miners of the henbane leaf. Bonnet ejected one of these, and watched it with his glass till it commenced a new tunnel, which it also enlarged with great expedition; and in order to verify the assertion of Réaumur, that they neither endeavour nor fear to meet one another, he introduced a second. Neither of them manifested any knowledge of the other's contiguity, but both worked hard at the gallery, as did a third and a fourth which he afterwards introduced; for though they seemed uneasy, they never attacked one another, as the solitary ones often do when they meet.*

BARK-MINING CATERPILLARS.

A very different order of mining caterpillars are the progeny of various beetles, which excavate their galleries in the soft inner bark of trees, or between it and the young wood (Alburnum). Some of these, though small, commit extensive ravages, as may readily be conceived when we are told that as many as eighty thousand are occasionally found on one tree. In 1783 the trees thus destroyed by the printer-beetle (Tomicus typographus, LATR.), so called from its tracks resembling letters, amounted to above a million and a half in the Hartz forest. It appears there periodically, and confines its ravages to the fir. This insect is said to have been found in the neighbourhood of London.

On taking off the bark of decaying poplars and willows, we have frequently met with the tracks of

Bonnet, Observ. sur les Insectes, vol. ii. p. 425.

a miner of this order, extending in tortuous pathways, about a quarter of an inch broad, for several feet and even yards in length. The excavation is not circular, but a compressed oval, and crammed throughout with a dark-coloured substance like sawdust-the excrement no doubt of the little miner, who is thereby protected from the attacks of staphylinide, and other predaceous insects, from behind. But though we have found a great number of these subcortical tracks, we have never discovered one of the miners, though they are very probably the grubs of the pretty musk-beetle (Cerambyx moschatus), which are so abundant in the neighbourhood of the trees in question, that the very air in summer is perfumed with their odour.*

Another capricorn-beetle of this family is no less destructive to bark in its perfect state, than the above are when grubs, as from its habit of eating round a tree, it cuts the course of the returning sap, and destroys it.

bark of a tree.

* J. R.

241

CHAPTER XIII.

Structures of Grasshoppers, Crickets, and Beetles.

GRASSHOPPERS, locusts, crickets, and beetles are, in many respects, no less interesting than the insects whose architectural proceedings we have already detailed. They do not, indeed, build any edifice for the accommodation of themselves or their progeny; but most, if not all of them, excavate retreats in walls or in the ground.

The house-cricket (Acheta domestica) is well known for its habit of picking out the mortar of ovens and kitchen fire-places, where it not only enjoys warmth, but can procure abundance of food. It is usually supposed that it feeds on bread. M. Latreille says it only eats insects, and it certainly thrives well in houses infested by the cockroach; but we have also known it eat and destroy lamb'swool stockings, and other woollen stuffs, hung near a fire to dry. It is evidently not fond of hard labour, but prefers those places where the mortar is already loosened, or at least is new, soft, and easily scooped out; and in this way it will dig covert ways from room to room. In summer, crickets often make excursions from the house to the neighbouring fields, and dwell in the crevices of rubbish, or the cracks made in the ground by dry weather, where they chirp as merrily as in the snuggest chimney-corner. Whe ther they ever dig retreats in such circumstances, we have not ascertained; though it is not improbable they may do so for the purpose of making nests.

P

M. Bory St. Vincent tells us, that the Spaniards are so fond of crickets, that they keep them in cages like singing-birds.*

THE MOLE-CRICKET.

The insect called, from its similarity of habits to the mole, the mole-cricket (Gryllotalpa vulgaris, LATR.), is but too well known in gardens, corn-fields, and the moist banks of rivers and ponds, in some parts of England, such as Wiltshire and Hampshire, though it is comparatively rare or unknown in others. It burrows in the ground, and forms extensive galleries similar to those of the mole, though smaller; and these may always be recognized by a slightlyelevated ridge of mould; for the insect does not throw up the earth in hillocks like the mole, but gradually, as it digs along, in the manner of the fieldmouse. In this way it commits great ravages, in hotbeds and in gardens, upon pease, young cabbages, and other vegetables, the roots of which it is said to devour. It is not improbable, we think, that, like its congener, the house-cricket, it may also prey upon underground insects, and undermine the plants to get at them, as the mole has been proved to do. Mr. Gould, indeed, fed a mole-cricket for several months upon ants.

The structure of the mole-cricket's arms and hands (if we may call them so) is admirably adapted for these operations, being both very strong, and moved by a peculiar apparatus of muscles. The breast is formed of a thick, hard, horny substance, which is further strengthened within by a double frame-work of strong gristle, in front of the extremities of which the shoulder-blades of the arms are firmly-jointed; a structure evidently intended to prevent the breast from being injured by the powerful action of the

*Dict. Classique d'Hist. Nat. Art. Grillon.

muscles of the arms in digging. The arms themselves are strong and broad, and the hand is furnished with four large sharp claws, pointing somewhat obliquely outwards, this being the direction in which it digs, throwing the earth on each side of its course. So strongly, indeed, does it throw out its arms, that we find it can thus easily support its own weight when held between the finger and thumb, as we have tried upon half a dozen of the living insects now in our possession.

The Mole Cricket, with a separate outline of one of its hands. The nest which the female constructs for her eggs, in the beginning of May, is well worthy of attention. The Rev. Mr. White, of Selborne, tells us that a gardener, at a house where he was on a visit, while mowing grass by the side of a canal, chanced to strike his seythe too deep, and pared off a large piece of turf, laying open to view an interesting scene of domestic economy. There was a pretty chamber dug in the clay, of the form and about the dimensions it