58 THE PHYSIOLOGY OF INSECT SENSES 



discharge is inhibited during inspiration. Some end-organs with fibres 

 in the segmental nerves respond to whistUng, ground tapping, and 

 respiration, others to sound only, others to respiratory movements 

 only. Those responding to sound are sharply tuned to about 100 c/s, 

 and the only parameter of the stimulus to which their frequency of 

 discharge is related is intensity. Since the segmental nerves from which 

 these signals were recorded are known to contain fibres from seg- 



FiG. 49. A segment of the 

 larva of Corethra 

 plumicornis showing 

 the location of one of 

 the segmental chordo- 

 tonal organs (C). (Re- 

 drawn from Graber, 

 1882.) 



mental chordotonal organs, it was suggested that they are the sensilla 

 involved in these activities (Hughes, 1952). Pumphrey (1940) also 

 suggested that the activity recorded from the segmental nerves of 

 locusts arises in chordotonal sensilla and not in hairs as formerly 

 believed (Pumphrey and Rawdon-Smith, 1936 c). It should be re- 

 membered, however, that the Type II neurons of stretch receptors are 

 also sensitive to respiratory movements and to periodic motion, so 

 that further investigation of chordotonal responses is needed. 



