THE GRASSHOPPER AND ITS ALLIES 



ground. Their eggs are laid loosely in these retreats. 

 They feed on plants and, if numerous, may be decidedly 

 injurious to vegetation. They make 

 a familiar chirping noise, the blended 

 sounds of which, as heard on a sum- 

 mer evening, rise and fall in a distinct 

 rhythm. The rate of chirp seems to be 

 entirely determined by temperature, so 

 that one may compute the temperature 

 by means of the formula 



^-40 



FIG. 1. Gryllus, 



, , cricket. Nat. size. 



Photo, by W. H. 



in which T stands for temperature, and 



N the number of chirps per minute. The mechanism by 



which the chirp is produced is as follows : Near the mid- 

 dle of each of the upper wings of 

 the male cricket is a vein so modi- 

 fied as to form a sort of file, and 

 near the margin of the wing is a 

 thickened scraper. When the up- 

 per wings are brought in contact 

 above the body, and the scraper of 

 one is rubbed across the file of the 

 other, the wings are set in vibration, 

 producing the call. 



An aberrant form of Gryllidee is 

 the mole cricket (Fig. 2), whose 



FIG. 2.--Grii!iuta?pa bore- f re f ee t have become much modi- 



alis, mole cricket. Nat. ne( j f ()r burrowing, 

 size. Photo, by W. H. 



C p 1 he Locustidae, 1 or long-horned 



1 From the Latin name for the locust and grasshopper, as well as the 

 lobster. 



