SOUND PERCEPTION IN LARV^ 149 



stimuli for such an organ is stressed, but the relative insensitivity 

 of the cercus of the cricket to all but the lowest frequencies, 

 together with the fact that the organ is frequently in contact with 

 the ground, leads these authors to suppose that its main function 

 here is to mediate the detection of earth-borne vibrations. In 

 the cockroach, where the cerci are carried upwardly inclined, it 

 seems likely that their function as wind gauges may be equal in 

 importance to their function as acoustic organs. They found 

 that there is a close parallel between the response in the cereal 

 nerve and that in the mammalian eighth nerve — a fact of con- 

 siderable physiological interest. 



It needs to be borne in mind that mechanical stimuli, appreciable 

 to man as touch and sound, probably intergrade as phases of 

 a single type of sensation in the majority of insects. Aerial 

 vibrations may be appreciated by those creatures through the 

 medium of generalised tactile receptors. In certain caterpillars 

 there is definite evidence that sound waves produce marked 

 responses when impinging upon their body-hairs. It has long- 

 been known that various lepidopterous larvae, and also those of 

 some Coleoptera, show evident indications of stimulation to 

 particular types of sounds. Minnich (1925), however, appears to 

 have been the first to locate the sense involved. He found that 

 larvae of Vanessa antiopa respond to appropriate sound stimuli 

 by throwing the anterior one-third of the body dorsally or dorso- 

 laterally. He used sounds produced by the human voice, piano, 

 organ, violin, Galton whistle, tone modulator, tuning forks and 

 by other means, and observed that the larvae responded in the 

 manner described in all cases except to the whistle and tone 

 modulator. The extent of the response varied according to the 

 intensity of the sound, and responses were obtained from vibrations 

 ranging from 32 to 1,024 per second. Decapitated bodies, and 

 fragments of bodies, will respond to sounds, and he concludes 

 that certain hairs, located chiefly in the anterior two-thirds of the 

 body, probably constitute the receptor organs involved. This 

 conclusion is based upon the fact that responsiveness to sounds 

 increases as the number of hairs increase in successive instars. 

 Partial destruction of the hairs by singeing either greatly reduces 



