IV. HOW THEY BECOME AWARE OF 

 THEIR SURROUNDINGS 



{Sight; hearing; touch; smell and taste) 



We take our own senses for granted, and look on things as being 'real' 

 only if we can see, hear, touch, smell or taste them. We know that other 

 people's senses never work in exactly the same way as our own: some 

 persons can hear the high-pitched sounds of bats or grasshoppers, to 

 which others are quite deaf; and we have only to consider the selection 

 of clothes worn by some people, to realise that their perception of colour 

 must differ widely from our own. Nevertheless, we instinctively trust 

 our own senses as a guide to what the world around us is really like, 

 and it is extremely difficult to put ourselves into the place of an animal 

 so far removed from us as an insect. 



If we stand in a sunny garden and watch bees flying in and out of a 

 hive, it is natural to think that they can see the garden as we see it; 

 that they pick out a promising blossom and fly to it in a purposeful way. 

 It needs an effort of will to put the human viewpoint out of mind, and 

 to enquire exactly how much the bee really knows of what is going on 

 round about. 



Let us look first at the senses of an insect, which give it messages 

 from the outside world, and then, in the next two chapters, let us see 

 how an insect may respond to these messages. 



Sight 

 The whole body surface of insects seems to be sensitive to light to some 

 extent, and those insects that Hve in caves and similar dark places may 

 be able to distinguish light from darkness, even though they have no 

 eyes. 



Normal sight in insects, however, depends on special organs, which 

 are of two kinds, compound eyes and simple eyes. 



Compound eyes are the principal organ of sight, the 'eyes' proper, of 

 adult insects. The outer surface of each eye consists of a number of 

 facets, varying from ten in some insects to over 20,000 in others. If 

 there are only a few facets these remain circular, but in most insects the 

 facets are tightly packed together, and are hexagonal, as in a honeycomb 

 (Figs. 69, 70). 



58 



