2Q2 ENTOMOLOGY 



Instinct, as distinguished from reason, attains adaptive ends without 

 prevision and without experience. For example, a butterfly selects a 

 particular species of plant upon which to lay her eggs. Caterpillars of 

 the same species construct the same kind of nest, though so isolated from 

 one another as to exclude the possibility of imitation. Every caterpillar 

 that pupates accomplishes the intricate process after the manner of its 

 kind, without the aid of experience. 



Instinctive actions belong to the reflex type they consist of co- 

 ordinated reflex acts. A complex instinctive action is a chain, each link 

 of which is a simple reflex act. In fact, no sharp line can be drawn be- 

 tween 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 en- 

 tirely 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 behavior 

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

 them, even when there is no evidence of its existence. An an illustration, 

 many plant-eating beetles, when disturbed, habitually drop to the ground 

 and may escape detection by remaining immovable. We cannot, how- 

 ever, 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 maintains, being, at the 

 same time, one of the simplest, most advantageous 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 Aristolockia, which 

 she cannot taste, in order to serve larvae, of whose existence she can have 

 no foreknowledge. Oviposition 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 neces- 

 sary incentive to any reflex act. The first movements of a larva within 



