306 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



Plate 3 



Fig. I. Tympanic nerve response in Prodenia cridania to a click of i.o msec, 

 duration at various intensities. The upper trace in each record shows the elec- 

 trical pulse which generated the click through a condenser transmitter. A, click 

 is near threshold intensity, and only i spike occurs in the more sensitive 

 acoustic unit. B, the same unit fires 3 times at increased click intensity. C, the 

 same unit fires 4 times. D, both acoustic units fire several times with spike 

 overlap at the highest intensity. Time may be judged from the square pulse 

 of 1.0 msec, duration. (From Roeder and Treat, 1957.) 



Fig. 2. Bilateral recording from the paired tympanic organs of Prodenia 

 eridania. Superimposed responses to i.o msec, clicks from condenser trans- 

 mitter. Clicks delivered at the beginning of trace. Upper trace from right 

 tympanic organ, lower from left organ. A, sound source on right side of moth. 

 B, sound source directly behind moth. C, sound source on left side. Time base, 

 1,000 cycles/sec. 



Plate 4 



Fig. I. Tympanic nerve response (upper trace) in Prodenia eridania to bat 

 cries simultaneously recorded with a condenser microphone (lower trace). The 

 bat (Eptesicus f, fusciis) was held i to 2 feet from the tympanic organ of the 

 moth. A, an audible "squeak" lasting several milliseconds. B, a shorter cry 

 containing ultrasonic frequencies. (From Roeder and Treat, 1957; details 

 loc. cit.) 



Fig. 2. The onset of flight in a calliphorid fly. Upper trace, movements of 

 thorax ; lower trace, potential changes in the thoracic muscles. Time marks, 

 10 msec, intervals. A platform under the feet of the fly was suddenly depressed. 

 Tarsal contact was lost at the lowest point on the upper trace, and the onset of 

 active wing beats are shown by the oscillations at the right in the upper trace. 

 (For further details see Roeder, 1951.) 



Plate 5 



Conduction in the nervous system of the cockroach Periplaneta americana. 



A, B, and C. A mechanical stimulus (M.ST.) was applied to the cercus. 

 The movement of the cercus appears as the first upward deflection on the upper 

 trace in A, B, and C. The lower trace in A, B, and C records the arrival of the 

 impulse volley at correspondingly labeled points in the diagram. 



D. An electric stimulus (E.ST.) o.i msec, in duration was given to nerve 

 3 close to the metathoracic ganglion. The electric response (lower trace) and 

 contraction (upper trace) of the extensor tibiae were recorded at point D. 



L.A., last abdominal ganglion; T3, metathoracic ganglion. Time marks for 

 A, B, and C, under C, 1.0 msec, intervals. Time marks for D, 1.0 msec, breaks 

 on upper trace. 



