SOUND RECEPTION 111 



bird which in turn is more sensitive than man (Schneider, 1950). 

 Flies are among the least-sensitive animals (Fig. 70). 



Pure vibrations at these high frequencies do not generally occur in 

 nature, but such high frequencies undoubtedly exist as transients in 

 the single pulse-hke vibrations of the substrate to which insects are 

 ordinarily exposed. Suddenness is the important factor, so perception 

 of these transients, even without frequency discrimination, may be 

 the contribution which the subgenual organs make to behaviour 

 (Autrum, 1959). 



