THE SENSES AND SENSE-OEGANS OF INSECTS. 179 



2. Telcesthetic senses, including, 



(d) Hearing : telling ns of certain states of distant 

 bodies through the intermediation of air-borne undu- 

 lations ranging up to some 36,000 per second. 



(e) The temperature sense : telling us of certain states 

 of distant bodies through the intermediation of efchcr- 

 bornc undulations of upwards of thirty million million 

 per second. 



(/) Sight : when the ether-borne undulations range be- 

 tween about 400 and 800 million million per second. 



The human organization is not fitted to respond to air- 

 borne undulations beyond about 36,000 per second, and this 

 upper limit of hearing varies considerably in different in- 

 dividuals. Nor does it respond to ether-borne undulations 

 below about thirty million million per second. Below about 

 400 million million and beyond about 800 million million 

 undulations per second tlie liuman eye perceives nothing, 

 the end-organs of sight are not stimulated. But photo- 

 graphy makes us indirectly acquainted with undulations up 

 to 1,600 million million per second. This may bo termed 

 the doctrine of limits in sensation. 



There would seem to be no organic reason why the senso- 

 organization of insects should have the same limits as that 

 of man. The probabilities are that the limits for them are 

 different, perhaps very widely different. Sir John Lubbock 

 has shown that ants are sensitive to ultra-violet iHys. It ia 

 quite conceivable that the ants' nest may resound with in- 

 sect voices inaudible to us, beyond our upper limit of hear- 

 ing. Moreover, while we hear sounds of different pitch, 

 and distinguish colours of different vibration-poriod, for ns 

 heat has neither tone nor colour. But it may be otherwise 

 with insects. It is conceivable that the long summer's day, 

 the warmth of which has for us neither tone nor colour, 



