INSECTS 



production of sound, they depend upon rasping and vibrat- 

 ing surfaces. The rasping surfaces are usually, as in the 

 instruments of the grasshoppers (Figs. 15, 16), parts of 

 the legs and the wings. The sound may be intensified, as 

 in the body of a stringed instrument, by special resonating 



areas, sometimes on 

 the wings, sometimes 

 on the body. The 

 cicadas, a group of 

 musical insects to be 

 described in a special 

 chapter, have large 

 drumheads in the wall 

 of the body with 

 which they produce 

 their shrill music. 

 They do not beat 

 these drums, but 

 cause them to vibrate 

 by muscles in the 

 body. The musical 

 members of the insect 

 families are in nearly 

 all cases the males, 

 and it is usually sup- 

 posed that they give 

 their concerts for the 

 purpose of engaging 

 the females, but that 

 this is so in all cases 

 we can not be certain. 

 The musical instru- 

 ments of the katydids 

 are quite different 

 from those of the 

 grasshoppers, being 

 situated on the over- 



Fig. 18. The front wings, or tegmina, of a 



meadow grasshopper, Orchelimum laticauda, 



illustrating the sound-making organs typical 



of the katydid family 



A, left front wing and basal part of right wing 

 of male, showing the four main veins: subcosta 

 (Sc), radius (/?), media (M), and cubitus (C«); 

 also the enlarged basal vibrating area, or 

 tympanum {Tm), of each wing, the thick file 

 vein (ft) on the left, and the scraper (s) on 



the right 



B, lower surface of base of left wing of male, 

 showing the file if) on under side of the file 



vein (A,fo) 



C, right front wing of female, which has no 

 sound-making organs, showing simple normal 



venation 



(34 



