68 VARIETY OF ORGANS OF SOUND AMONG BEETLES. 



(2) Prosternum on Mesosternum {Omaloplia 



hrunnea). 



(3) Elytra with rasp at the end (Curculionida ; 



Dytiscida, Pelobius). 



(4) Cox8e with rasp (Geotrupes, Ceratophyus). 



(5) Cover-margin rasp rubbing against the thigh 



( Ghiasognath us Gra ntii) . 



(6) Pygidium with two rasps in the middle 



(Crioceris, Lema, Copris, Oryctes, Necro- 

 phorus, Tenebrionida). 



(7) Abdomen with a grating-ridge and four 



grating-plates (Trox sabulosiis), 



(8) Abdomen with two toothed ridges rubbing 



on cover-margin rasp (Elaphrus, Blethisa, 

 Cychrus). 



(9) Elyti-a rubbing with under-wing rasp {PeloUus 



Herrmanni), 



(10) Wings rubbing against abdominal ringlets 

 (Melolontha fullo) „ 



5. Exploding sounds from the tail (Brachinus). 



6. Sounds produced by the spiracles (Melolontha). 

 Graber, moreover, has shown by a number of 



interesting experiments * that the power of hearing is 

 by no means confined to those beetles which are known 

 to produce sounds themselves. 



Passing on to other groups of insects, flies and gnats, 

 besides the humming of the wings, produce sounds, 

 like the cockchafer, through the spiracles, some of 

 which are especially arranged for this purpose. If a 

 fly be caught and held between the fingers, it will 

 generally make a loud and peculiar sound. The hum 

 of the mosquito is only too familiar to most of us. 



* "Die Chordotoual Siuuesorgaue der lusekteu," Arch, fiir Mic. 

 Anal, 1882. 



