THE INSECTS: HEXAPODA 97 



the insect in much the same way that similar organs serve 

 man. Experiments prove conclusively that insects feel, 

 see, hear, taste, smell, and we know that they are able to 

 recognize differences in temperature. But the remarkable 

 thing is that many insects have additional sense organs 

 which we are entirely unable to interpret because we have 

 nothing like them in our own bodies. In studying other 

 animals we are limited by our understanding of our own 

 senses, and find it hard to appreciate the fact that what we 

 see with our eyes and hear with our ears may not be exactly 

 the same as effects produced on the nervous system of 

 another animal. As human beings we view our own actions 

 in the light of intelligence. When we attempt to explain the 

 actions of other people or of other animals, it is only with 

 difficulty that we can interpret on the basis of what we 

 actually observe. When a man is lost in the woods at night 

 he walks toward any light, reasoning that he may find help. 

 But this does not make it safe to assume that a moth flies 

 toward a light because of any intelligent motive. In fact 

 the movement of the moth in this instance is involuntary. 



Most of the actions of insects are purely reflex, involving 

 none of the higher types of mental activity known as intelli- 

 gence. When a stimulus acts upon an insect and causes the 

 body to take a definite position there is no choice of action 

 on the part of the insect. The response under these condi- 

 tions is called a tropism. Tropisms are purely mechanical 

 or involuntary responses to a stimulus, not involving intelli- 

 gent choice of action. 



It is difficult to draw the line between these automatic 

 reflexes and the acts which are spoken of as instinctive. An 

 instinctive act is one which an individual performs without 

 ever having been taught. When a wasp paralyzes spiders 

 and places them in her nest to serve as food for her unborn 

 young there is small possibility that she has any prevision 



