SENSES OF INSECTS. 4? 



dangers ; the truth of which latter conclusion is demonstrated by 

 the fact that, if the disturbing element continues, the rapping will 

 after a time grow less, until it will be found that all the termites 

 have retired underground. If this be so, it is evident that the 

 striking must be perceived by the workers in some way. Per- 

 sonally, I think they hear it, though this is almost impossible to 

 prove; for I can no more believe that they perceive it by the 

 sense of touch, as we understand it, than that a man can perceive 

 the striking of distant horse-hoofs by means of his hands rather 

 than his ears. The soldiers, however, do not stand on such 

 debateable ground, as they are able to give some evidence of their 

 perceptions. It must be remembered that they are blind, and 

 now Mr. Arkle asserts them to be deaf, thus leaving them only 

 the senses of touch and smell wherewith to perceive the 

 approach of their enemies. This seems to be improbable on the 

 face of it, and I have had abundant proof that it is not the case. 

 When the footstep of the observer falls within a certain distance 

 of the termites, the little army becomes much perturbed, and the 

 warning rap is energetically repeated every few seconds. If there 

 be a fairly long row of them at work, the rap may be distinctly 

 heard to travel along the line from its starting-point. However, 

 unless again disturbed, they will soon quiet down. Then if the 

 hands be clapped, the fingers snapped, a dry stick cracked, or any 

 other similar sound made within a foot or two of the insects, the 

 sentinels will give a sharp rap after each noise. Now I have made 

 these experiments very many times, and always with the same 

 result ; therefore this cannot be regarded as a mere coincidence. 

 It may then be granted that the insects are affected by and can 

 perceive these sounds ; in which case they must be able to hear, 

 as that is the only sense by which they could perceive them. The 

 sound that I have found to elicit the most prompt and energetic 

 reply is a sharp whistle, care of course being taken to prevent the 

 breath reaching the termites. I have known them to hear such 

 a whistle at a distance of even six feet, which, if proportionate 

 size be taken as a standard, would mean about half a mile in man. 

 This example is, I think, sufficient to show the fallacy of 

 Mr. Arkle's assertion that any hearing powers insects may 

 possess are rudimentary, and of no use for warning purposes. 



But since it has been shown that the cicada, with a complicated 

 sound-producing organ, and the termite with none, are both 

 equally capable of hearing, we have good reason for assuming that 

 insects in general are possessed of the same power, and especially 

 those that are themselves able to produce sound. 



With regard to the more speculative issue, as to whether 

 insects possess some additional sense which we have not, Mr. 

 Arkle says that if they have such a sense it is obviously one of 

 direction* In the first place, the obviousness is by no means 

 apparent to me j and, secondly, as we do possess a sense of 

 direction, it hardly seems to come within the scope of the 



