THE EXTERNAL ANATOMY OF INSECTS 



S3 



B 



places itself in a nearly horizontal position, and raising both hind legs 

 at once rasps the femora against the outer surface of the wings. The 



most common representatives of insects that 

 stridulate in this way belong to the genus Steno- 

 bothrus. 



The stridulating organs of the Gryllidae and 

 the Locustidae. The stridulating organs of the 

 Gryllidae and the Locustidae are of the same type, 

 and are the most highly specialized found in the 

 Orthoptera. They consist of modified portions of 

 the fore wings; both the vibrating and the rasping 

 elements of the organs pertaining to the wings. 



It is by rubbing the two fore wings together 

 that sound is produced. 



In what is probably the more generalized con- 

 dition of the organs, as seen in Gryllus, each 

 fore wing bears a rasping organ, the file (Fig. 

 94, /) a hardened area, the scraper (Fig. 94, s), 

 .^.*i l^..' 4L-, against which the file of the other wing acts, and 

 vibrating areas, the tympana (Fig. 94, t, t). As 

 the file of either wing can be used to set the 

 tympana of the wings in vibration, we may say 



Fig. 94. Fore wing of that Gryllus is ambidextrous. 

 Gryllus: A, as seen . . 



from above, that When the cricket wishes to make his call, he 



part of the wing e i ev ates his fore wings so that they make an angle 

 which is bent down . , " , , , 



on the side of the of about forty-five degrees with the body; then 



abdomen is not holding them in such a position that the scraper 

 shown; s, scraper;/, , , 



/, tympana. B.base of one rests on the file of the other, he moves the 



of wing seen from w i nRS back and forth laterally, so that the file and 

 below; s, scraper; , , . , , 



f, file. C, file great- scraper rasp upon each other. .his throws 



ly enlarged. wings into vibration and produces the call. 



It is easy to observe the chirping of crickets. If one will move 

 slowly towards a cricket that is making his call, and stop when the 

 cricket stops chirping until he gains confidence and begins again, 

 one can get sufficiently near to see the operation clearly. This can 

 be done either in the day time or at night with the aid of a light. 



The songs of the different genera of crickets can be easily dis- 

 tinguished, and that of each species, with more care. Writers on the 

 Orthoptera have carefully described the songs of our more common 

 cr'clicts, and especially thoseof the tree crickets. The rate of chirping 



