190 Heredity. 



and altlioiigli the general cliaracter of the sound, and its 

 mcclianical cause, arc essentially alike in all of them, the 

 position and character of the sound-producing mechan- 

 ism varies greatly. 



In the male cricket the under surface of each wing- 

 cover hasa row of sharp transverse ridges or teeth, which 

 is rapidly scraped across a projecting ridge on the outer 

 surface of the opposite wing, thus producing the music. 

 First one wing is rubhed over the other, and then the 

 movement is reversed. Both wings are raised a little at 

 the same time, so as to increase the resonance. 



In the Locustidse the opposite Aving-covcrs differ in 

 structure, and their action cannot be reversed, as it is in 

 the crickets. The left wing acts as the bow, and is 

 scraped over the right, which serves as the fiddle. In 

 some forms the posterior part of the pro-thorax is ele- 

 vated into a sort of resonating dome over the wing-cov- 

 ers. In the grasshoppers the sound is produced in a 

 very different manner. There is usually a long row of 

 nearly a hundred minute teeth on the inner surface of 

 the femur, and this is scraped across the sharp pro- 

 jecting nervures on the wing-covers. 



In one South African form the femur is rubbed, not 

 against the wing-cover, but against a notched ridge on 

 the side of the abdomen, and the whole abdomen of the 

 male is distended with air, like a great bladder, to in- 

 crease the resonance. 



The female grasshopper has the stridulating apparatus 

 in a rudimentary condition, audit is interesting to note 

 that the young male is like the adult female in tliis 

 respect, for Landois states that the teeth on the femora 

 of the female remain throughout life in the condition 

 in which they appear in both sexes during the larval 

 state, but in the male they become fully develoj^ed and 



