The Decticus: his Instrument 



surface of the left wing-case, overlapping 

 the right, which is furnished with the 

 tympanum; all, lastly, have a thin, faint trill 

 which is sometimes hardly perceptible. 



One alcne, modifying the details of the 

 apparatus without introducing any innovation 

 into the general structure, achieves a certain 

 power of sound. This is the Vine Ephip- 

 piger, who does without wings and reduces 

 his wing-cases to two concave scales, ele- 

 gantly fluted and fitting one into the other. 

 These two disks are all that remains of the 

 organs of flight, which have become ex- 

 clusively organs of song. The insect aban- 

 dons flying to devote itself the better to 

 stridulation. 



It shelters its instrument under a sort of 

 dome formed by the corselet, which is curved 

 saddlewise. As usual, the left scale occupies 

 the upper position and bears on its lower 

 surface a file in which we can distinguish with 

 the lens eighty transversal denticulations, 

 more powerful and more clearly cut than 

 those possessed by any other of the Grass- 

 hopper tribe. The right scale is underneath. 

 At the top of its slightly flattened dome, the 

 mirror gleams, framed in a strong nervure. 



For elegance of structure, this instrument 



267 



