considerable time. In ordinary cases, they traverse but short spaces at a time; but when any change of place becomes requisite, they are able, like their relatives the locusts, to fly both high and far. Indeed, it is very probable that the relations given by travellers respecting the immense congregations and flights of what are vaguely termed locusts, ought sometimes to be referred to certain kinds of Gryllidæ.
Although these insects do not leap so powerfully as the true locusts, the structure of the hinder legs, the instruments by which they accomplish it, is precisely similar. The thigh is much elongated, and thickens gradually as it approaches the body; the knee is likewise a little swollen to afford room for the somewhat complex articulation which unites it to the tibia. Along each side of the thighs, are three longitudinal ridges, and on the upper and under sides, a double row of quadrangular elevations, placed obliquely, and somewhat resembling the surface produced by plaiting together two pretty broad thongs. What may be called the knee-pan, has a cavity in the centre, adapted for the reception of the head of the tibia, and in this sinus the condyle of the tibia works. Besides the central process or condyle of the tibia, there are two lateral ones which also work in a sinus of the knee. The motion of the tibia is therefore semirotatory up and down, as upon a pair of pivots, and all the parts being connected by means of strong ligaments, dislocation cannot easily take place. When this is considered in connection with the state of the muscles of the thigh, thickened for
