Smithsonian Report, 1961. — -Roeder and Treat 



PUATE 2 



1. Diagram of the tympanic organ of a noctuid moth. The sensillum (S) contains the 

 pair of acoustic receptors or A cells. The A nerve fibers are joined by that of the B cell 

 (BJx) to form the tympanic nerve (IIINIb). TAS, tympanic air sac; B and SP, 

 skeletal supports; TM, tympanic membrane. (After Treat and Roeder, 1959.) 



. Tympanic nerve response in Prodenia eridania to a pure tone of 40 kc. The occasional 

 large spikes originate in the B cell. {A) Response to a sound intensity close to the 

 threshold of the sensitive A cell. {B) Intensity 7 db above that in {A). (C) Intensity 

 15 db above that in {A). (D) Intensity 23 db above that in (A). The less sensitive 

 A cell discharges occasionally in (C), and frequently in (D), as indicated by the double 

 peaks. Time line 100 msec. (From Roeder, 1959.) 



