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 



JV_4Q FIG. 1. Gryllus, 



J- = 50 -j , cricket. Nat. size. 



Photo, by W. H. 



in which T stands for temperature, and c - p - 



N the number of chirps per minute. The mechanism by 



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



1 die of each of the upper wings of 



the male cricket is a vein so modi- 



lkJl& fied as to form a sort of file, and 



^1 B4 near tne margin of the wing is a 



^.^^HjN^ thickened scraper. When the up- 



*^B^P per wings are brought in contact 



^^ jM above the body, and the scraper of 



^^ fH^^^*"* one * s ru bked across the file of the 



tjSf other, the wings are set in vibration, 



ylf producing the call. 



Jf . An aberrant form of Gryllidse is 



the mole cricket (Fig. 2), whose 

 fore feet have become much modi- 

 fied for burrowing. 



The Locustidae, 1 or long-horned 



FIG. 2. Gryllotalpa bore- 

 alis, mole cricket. Nat. 

 size. Photo, by W. H. 

 C. P. 



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

 lobster. 



