GRYLLIDiE. 
251 
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 re- 
latives the locusts, to fly both high and far. Indeed, 
it is very probable that the relations given by travel- 
lers respecting the immense congregations and flights 
of what are vaguely termed locusts, ought sometimes 
to be referred to certain kinds of Gryllidce. 
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 pre- 
cisely 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 w'hich 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 pro- 
duced 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 there- 
fore 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 
