150 THE SENSE ORGANS AND REFLEX BEHAVIOUR 



or abolishes the response ; heavy loading of the hairs with line 

 droplets of water, or with flour particles, produces a similar effect. 

 During ecdysis, when the old hairs are more or less disconnected 

 from the underlying parts and the new hairs are not yet functional, 

 the response is either feeble or nil. Larvai subjected to a tone 

 stimulus of short duration, repeated at intervals of five seconds, 

 showed little or no fatigue in the course of 100 trials. Individuals 

 subjected to continuous tone stimulation, however, generally 

 became fatigued and ceased to respond after a period ranging 

 from five to sixty seconds. Minnich further observed that 

 continuous air currents inhibit the response to sounds. This is 

 due, in general, to one form of stimulation inhibiting the response 

 to another kind. When the air current is prolonged, however, 

 another factor, probably that of fatigue, also becomes involved, 

 Larvse fatigued to C (256 V/S) or G (384 V/S) will not respond to 

 C (512 V/S). When fatigued to C, however, larvae still gave 

 100 per cent, response to C and about 50 per cent, response to G. 

 These results suggest the tentative conclusion that hairs of 

 different lengths are affected by the various pitches of sound 

 indicated. Abbott (1927) carried out very similar observations 

 with larvae of the moth Datana (fam. Notodontidae). Definite 

 responses were noted to air currents, sudden jars, and to the two 

 notes only, viz., C" (512 V/S) and F sharp (728 V/S) ; larvae thus 

 stimulated elevated the anterior and posterior regions of the 

 body. During the experiments the larvae were protected from 

 air currents : they were several feet from the instruments used, 

 and vibrations from the substratum were eliminated. No 

 responses were observed when the body-hairs were coated with 

 water or shellac, or when the body-surface was anaesthetised with 

 a 2 per cent, solution of procain. Baier (1930) has also shown that 

 larvae of Pieris rapce react to certain acoustic stimuli in much the 

 same manner as those of Datana. His experiments, however, 

 were by no means extensive, but he showed that when stimulated 

 by a whistle or by vocal means the extent of the reaction varied 

 directly with the nearness of the stimulus, its intensity and its 

 suddenness. The fact that larvae whose body-hairs had been 

 entangled with cotton fibres responded very feebly, and when 



