SOUND RECEPTION 95 



more, species in which tympanic organs are not known to occur on 

 the body are somewhat sensitive to sound. For example, the satyrid 

 butterfly Cercyonis pegala responds to air-borne sounds of high 

 intensity (100-1 10 db). It should be remembered, however, that there 

 exist on the ventral surface of the basis of the wings of this insect 

 chordotonal sensilla associated with minute tympanic membranes 

 (Vogel, 1912), and some people have tendered the suggestion that 

 sound reception by these organs is possible (Vogel, 1912; Pringle, 

 1957). 



The tympanic organ is sensitive to very high sound frequencies. Res- 

 ponses in the frequency range 3,000-20,000 c/s have been recorded 

 from the tympanic nerves of the moths Phalera bucephala (Notodon- 

 tidae) and Arctia caja (Arctiidae) (Haskell and Belton, 1956). The very 

 thorough investigations of Roeder and Treat (1957, 1959, 1961a, 

 1961b) with a number of noctuids have shown that the sensitivity 

 extends up to stimulus frequencies of 100,000 c/s. These investigations 

 have also revealed many of the characteristics of these organs. A rest- 

 ing discharge occurs at the ordinary noise level of the laboratory. It 



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Fig. 65. Tympanic nerve activity in the noctuid Prodenia eridania. A, 

 activity in the tympanic nerve at laboratory noise level. The large spike 

 belongs to the non-acoustic unit. B, response in one acoustic unit to 

 continuous sound of 70 kc/s. C, response in both acoustic units to 

 30 kc/s. Time marks, 100 c/s. (Courtesy of Roeder and Treat.) 



