96 THE BIOLOGY OF INSECTS 



result in each case follows certainly, so that the behaviour 

 of a bee among blossoms may on this interpretation be 

 strictly compared to ** the behaviour of iron filings in the 

 magnetic field." On this view the observable actions of an 

 insect depend altogether upon the kinds of stimulation to 

 which it may be subjected, along with the innate tendency 

 of its tissues and organs to respond to such stimulations in 

 particular ways. A moth flies into the candle flame that 

 destroys its life, because it must needs react to a source of 

 light by way of direct approach. And on the other hand, 

 a female housefly makes for a heap of refuse and lays her 

 eggs therein, because the smell of the refuse is an attraction, 

 and the nerve impulses pass on to the centres that control 

 the actions of the genital ducts and ovipositor, so that the 

 laying of eggs is part of the bundle of reflexes, which in 

 this case leads not to the curtailment of the insect's life but 

 to the perpetuation of its race. Such insect activities as 

 can be explained by this simple ** tropic " formula may 

 therefore be either harmful or beneficial to the species. 

 What impresses the thoughtful observer is that if strikingly 

 adaptive actions are the result of simple reflexes, there 

 remains the further question why the combined reflexes 

 work out to a beneficial end ? While the study of tropisms 

 undoubtedly helps the naturalist to analyse the activities of 

 insects, it appears that the explanation of all kinds of insect 

 behaviour as due to these reactions maybe deceptively simple. 

 The observer who attributes to an insect motives and states 

 of consciousness like his own, because he sees a moth fly 

 towards a lamp or an ant scuttle into a burrow, is misled by 

 false analogies of behaviour. But such an observer at least 

 recognises that the insect that he watches is alive, while the 

 rigid follower of the tropic explanation, who is certain that 

 all the creature's actions are inevitably determined by the 

 nature of the stimulations from without that affect its 

 nervous system or act directly on its various tissues, seems 

 to overlook those stimulations which may originate within 

 the organism and give rise to aspects of behaviour un- 

 foreseen and inexplicable. 



