314 ENTOMOLOGY 



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 behavior 

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

 them, even when there is no evidence of its existence. As an illustra- 

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

 ground and may escape detection by remaining immovable. We 

 cannot, however, believe that these insects "feign death" with any con- 

 sciousness 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 Aristolochia, which 

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

 no foreknowledge. Oviposition is here an instinctive act, really a 

 chemotropism, which is not performed until it is evoked by some sort 

 of stimulus probably an olfactory one from a particular kind of plant. 



Stimuli. Some determinate sensory stimulus is, indeed, the neces- 

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

 the egg-shell are doubtless due to a sensation, probably one of tem- 

 perature. Simple contact with the egg-shell is probably sufficient to 

 stimulate the jaws to work, and the caterpillar eats its way out; yet it 

 cannot foresee that its biting is to result in its liberation. Nor, later on, 

 when voraciously devouring leaves, can the caterpillar be supposed to 

 know that it is storing up a reserve supply of food for the distant period 

 of pupation and the subsequent imaginal stage. The ends of these 

 reflex actions are proximate and not ultimate, except from the stand- 

 point of higher intelligence. 



Just as simple reflexes link together to form an instinctive action, so 

 may instincts themselves combine. The complex behavior of a solitary 

 wasp is a chain of instincts, as the Peckhams have shown. All the opera- 

 tions of making the nest, stinging the prey, carrying it to the nest, etc., 



