INSECT BEHAVIOR 357 



chain, each link of which is a simple reflex act. In fact, no 

 sharp line can be drawn between reflexive and instinctive 

 actions. 



Basis of Instinct. Reflex acts, the elements from which 

 instinctive actions are compounded, are the inevitable responses 

 of particular organs to appropriate stimuli, and involve no 

 volition. The presence of an organ normally implies the 

 ability to use it. The newly born butterfly needs no practice 

 preliminary to flight. The process of stinging is entirely 

 reflex ; a decapitated wasp retains the power to sting, directing 

 its weapon toward any part of the body that is irritated; and 

 a freshly emerged wasp, without any practice, performs the 

 stinging movements with greatest precision. 



As Whitman observes, the roots of instincts are to be sought 

 in the constitutional activities of protoplasm. 



Apparent Rationality. The ostensible rationality of be- 

 havior among insects, as was said, often leads one to attribute 

 intelligence to them, even when there is no evidence of its 

 existence. As an illustration, many plant-eating beetles, when 

 disturbed, habitually drop to the ground and may escape detec- 

 tion by remaining immovable. We cannot, however, believe 

 that these insects " feign death " with any consciousness of 

 the benefit thus to be derived. This act, widespread among 

 animals in general, is instinctive, or reflex, as Whitman main- 

 tains, being, at the same time, one of the simplest, most advan- 

 tageous and deeply seated of all instinctive performances. 



Take the many cases in which an insect lays her eggs upon 

 only one species of plant. The philenor butterfly hunts out 

 Aristolochia, which she cannot taste, in order to serve larvae, 

 of whose existence she can have no foreknowledge. Oviposi- 

 tion is here an instinctive act, not performed until it is evoked 

 by some sort of stimulus perhaps an olfactory one from a 

 particular kind of plant. 



Stimuli. Some determinate sensory stimulus, indeed, is the 

 necessary incentive to any reflex act. The first movements of 

 a larva within the egg-shell are doubtless due to a sensation, 



