The Gryllidae possess a pair of tympana on each front leg, but these organs contrast with those of the Locustidae in that the pair on each leg usually differ from one another, the one on the outer or posterior aspect being larger than that on the inner or front face of the leg. The ears of the Gryllidae have not been so well investigated as those of the Locustidae, but are apparently of a much less perfect nature. No orifice for the admission of air other than that of the prothoracic stigma has been detected, except in _Gryllotalpa_. On the other hand, it is said[260] that in addition to the tibial organs another pair of tympana exists, and is seated on the second abdominal segment in a position analogous to that occupied by the ear on the first segment of Acridiidae. The musical powers of the crickets are remarkable, and are familiar to all in Europe, as the performance of the house-cricket gives a fair idea of them. Some of the Insects of the family are able to make a very piercing noise, the note of _Brachytrypes megacephalus_ having been heard, it is said, at a distance of a mile from where it was being produced. The mode of {333}production is the same as in the Locustidae, rapid vibration of the tegmina causing the edge of one of them to act on the file of the other. The mole-cricket, _Gryllotalpa vulgaris_—the _Werre_ of the Germans, _Courtilière_ of the French—is placed with a few allies in a special group, Gryllotalpides, characterised by the dilated front legs, which are admirably adapted for working underground. Like the mole, this Insect has a subterranean existence. It travels in burrows of its own formation, and it also forms beneath the surface a habitation for its eggs and family. Its habits have been alluded to by Gilbert White,[261] who tells us that "a gardener at a house where I was on a visit, happening to be mowing, on the 6th of May, by the side of a canal, his scythe struck too deep, pared off a large piece of turf, and laid open to view a curious scene of domestic economy: there were many caverns and winding passages leading to a kind of chamber, neatly smoothed and rounded, and about the size of a moderate snuff-box. Within this secret nursery were deposited near a hundred eggs of a dirty yellow colour, and enveloped in a tough skin, but too lately excluded to contain any rudiments of young, being full of a viscous substance. The eggs lay but shallow, and within the influence of the sun, just under a little heap of fresh moved mould like that which is raised by ants." [Illustration: FIG. 206.—Front leg of the mole-cricket. A, outer; B, inner aspect: _e_, ear-slit.]