THE EXTERNAL ANATOMY OF INSECTS 



83 



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 Tettigoniidae. — The stridulating organs of 

 the Gryllidae and the Tettigoniidae 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 rasp- 

 ing 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 Gryllns, each 

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

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

 \:,^^^^^^ 1,^-4^ against which the file of the other wing acts, and 

 'Itli 'Eli 1:1:^0 vibrating areas, the tympana (Fig. 94, /, t). As 

 rm^^?^' ^?^^ '^^ ^ the file of either wing can be used to set the 

 C tympana of the wings in vibration, we may say 



Fig.94.— Fore wing of that Grylliis is ambidextrous. 



Grvllus; A, as seen 1 , • 1,1 



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



part of the wmg elevates his fore wings so that thev make an angle 

 which IS bent down ^° .'i,, , 



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; 5, scraper;/, , „, ^ , - , 



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



of wing seen from ^^jngg ^^ck and forth laterally, so that the file and 

 below; s, scraper; , , ^, . , 



/.file. C, file great- scraper rasp upon each other. Ihis throws the 

 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 

 crickets, and especially those of the tree crickets. The rate of chirping 



