90 THE PHYSIOLOGY OF INSECT SENSES 



(1941), who recorded from legs in which the subgenual organs pre- 

 sumably had been destroyed. Unfortunately, the precision of the 

 operation was not confirmed histologically post mortem. In any event, 

 the sensitivity to air-borne sound waves extended from 1,000 c/s to the 

 upper limits of the stimulation apparatus (10,000 c/s). The higher the 

 frequency, the lower the threshold. Responses at frequencies below 

 1,000 c/s were obtained only by employing intensities so high that it is 

 doubtful that they truly fell within a physiological range. 



The abdominal tympanic organs of two acridids {Locusta migratoria 

 migratorioides and Arphia sulphured) were sensitive over the range 

 300-10,000 c/s (Wever, 1935; Pumphrey and Rawdon-Smith, 1936 b) 



30 — 



o 



V 



<u 

 c 



o 

 o 



\) 



U 



c 



t 



TO 



■^ 

 C 

 03 



CU 



o 



c 

 o 



30 



60 



90 



300 



3,000 



10.000 



Frequency (c/sec) 



Fig. 63. a, Threshold curve for tympanic organs of Arphia sulphurea 

 averaged from Wever's figures, b, Threshold curve for an isolated 

 tympanic organ of Locusta. c, Human threshold subjectively de- 

 termined (from Wegel, 1932). (Redrawn from Pumphrey, 1940.) 



