252 THE LOWER AMAZONS. Chap. VI. 



on the under side is crossed by a number of fine 

 sharp furrows like those of a file. When the insect 

 rapidly moves its wings, the file of the one lobe is 

 scraped sharply across the homy margin of the other, 

 thus producing the sounds ; the parchmenty wing-cases 

 and the hoUow drum-like space which they enclose 

 assisting to give resonance to the tones. The project- 

 ing portions of both wing-cases are traversed by a similar 

 strong nervure, but this is scored like a file only in 

 one of them, in the other remaining perfectly smooth. 

 Other species of the family to which the Tanana belongs 

 have similar stridulating organs, but in none are these 

 so highly developed as in this insect ; they exist always 

 in the males only, the other sex having the edges of 

 the wing-cases quite straight and simple. The mode 

 of producing the sounds and their object have been 

 investigated by several authors with regard to certain 

 European species. They are the call-notes of the males. 

 In the common field-cricket of Europe the male has 

 been observed to place itself, in the evening, at the 

 entrance of its buiTow, and stridulate until a female 

 approaches, when the louder notes are succeeded by 

 a more subdued tone, whilst the successful musician 

 caresses with his antennae the mate he has won. Any 

 one who will take the trouble may observe a similar 

 proceeding in the common house-cricket. The nature 

 and object of this insect music are more unifomi than 

 the structure and situation of the instrument by which 

 it is produced. This differs in each of the three allied 

 families above mentioned. In the crickets the wing- 

 cases are symmetrical ; both have straight edges and 



