The Mole Crickets are distinguished from all other insects by the structure of their fore-legs, which are wide and indented, in such a manner as to resemble a hand, analogous to that of the mole. This leg betrays the habits of the cricket much better than our hands betray ours. They make use of them, indeed, as spades, with which they hollow out subterranean galleries, and accumulate at the side of the entrance-hole the rubbish thus drawn out. The French name comes from the old French word courtille, which means garden. Such places and vineyards are the favourite haunts of these destructive insects.
If the Mole Crickets, or Courtilières, have spades on their front legs, their hind-legs are very little developed, so that it would be perfectly impossible for them to jump, particularly as their large abdomen would hinder their so doing. The wings are broad, and fold back in the form of a fan; they make little use of them, and it is only at night-fall that the mole cricket is seen to disport himself, describing curves of no great height in the air. It is found principally in cultivated land, kitchen-gardens, nursery gardens, wheat fields, &c., where it scoops out for itself an oval cavity communicating with the surface by a vertical hole ([Fig. 306]). On this hole abut numerous horizontal galleries, more or less inclined, which permit the insect to gain its retreat by a great many roads, when pursued.
It is easy to understand that an insect which undermines land in this way must cause great damage to cultivation. Whether the crops serve it for food or not, they are not the less destroyed by its underground burrowings. Lands infested by the mole cricket are recognisable by the colour of the vegetation, which is yellow and withered; and the rubbish which these miners heap up at the side of the openings leading to their galleries, resembling mole-hills in miniature, betray their presence to the farmer. To destroy them, they pour water or other liquids into their nests, or else they bury, at different distances, vessels filled with water, in which they drown themselves. From the month of April the males betake themselves to the entrance of their burrows, and make their cry of appeal. Their notes are slow, vibrating, and monotonous, and repeated for a long time without interruption, and somewhat resembling the cry of the owl or the goat-sucker.
Fig. 306.—The nest of the Mole Cricket
(Gryllo-talpa vulgaris).
The female lays her eggs, to the number of from two to three hundred, in the interior of a sort of chamber scooped out in soil stiff enough to resist the action of rain. The hatching takes place at the end of a month.
It is not till the following spring that the larvæ pass into the pupa state, and that the organs of flight begin to be marked out. According to M. Féburier, three years are required for the complete development of the mole cricket, which is a fact that indicates remarkable longevity in these insects. All authors agree, moreover, in extolling the solicitude with which the mole cricket takes care of her little ones. She watches over them, and, they say, procures them food.
The genus Tridactylus, which bears a great analogy to the mole cricket, is the smallest genus of Orthoptera known; the species are not more than a sixth of an inch in length, and are found in the south of France, on the banks of the Rhône and other rivers, where they disport themselves in sand exposed to the sun. The Tridactyli leap with remarkable agility, even on the surface of the water, for their legs are provided with flat appendages much resembling battledores.