82 



AN INTRODUCTION TO ENTOMOLOGY 



In each of these famiHes the vibrating element of the stridulating 

 organ is a portion of one or of both of the fore wings ; but this is set in 

 motion in several different ways. In some exotic Acridiidas abdominal 

 stridulating organs exist. 



The stridulating organs of the Locustidae. — With many species 

 of the Locustidffi we find the males furnished with stridulating organs ; 

 but these are comparatively simple, and are used only in the day time. 

 Two methods of stridulation are used by members of this family. 

 The simpler of these two methods is employed by several common 

 species belonging to the (Edipodinae; one of which is the Carolina 

 locust, Dissosteira Carolina, whose crackling flight is a common feature 

 of country roadsides. These locusts, as they fly, rub the upper sur- 

 face of the costal margin of the hind wings upon the lower surface of 

 the thickened veins of the fore wings, and thus produce a loud but not 

 musical sound. 



The second method of stridulation practiced by locusts consists 

 in rubbing the inner surface of the hind femora, upon each of which 

 there is a series of bead-like prominences (Fig. 92), against the outer 



surface of the fore wings. 

 With these insects, there is a 

 thickening of the radius in the 

 basal third of each fore wing, 

 and a widening of the two 

 areas between this vein and 

 the costal margin of the wing, 

 which serves as a sounding 

 board (Fig. 93). The two 

 wings and femora constitute a 

 pair of violin-like organs; the thickened radius in each case cor- 

 responding to the strings; the membrane of the wing, to the body 

 of the instrument ; and the file of the femur, to the bow. These two 

 organs are used simultaneously. When about to stridulate, the insect 



B-- 



Fig. 92. — A, hind femora of Stenobothrus ; 

 B, file greatly enlarged. 



Fig- 93- — Fore wing of a male of Stenobothrus. R, radius; Sc, subcosta; 

 C, costa. 



