CHAPTER V 



The Behavior of Insects 



Most of the movements of insects are automatic responses to a 

 direct external stimulus. For example, ants of certain species always 

 move away from the hght ;- flies, toward it. Roaches will attempt to 

 crowd into narrow crevices, where their body is in close contact all 

 around with the surrounding substance. Some kinds of caterpillars 

 habitually crawl toward the ends of twigs, or contrary to gravity. 

 Aquatic insects move toward water. 



Most of the movements of insects, if carefully analyzed, will be 

 found explainable as some of these simple reactions. But there is 

 another group of movements that are really complex. An example 

 is seen in the spinning of its cocoon by a caterpillar. Here we have 

 genuine evidence of the workings of ' instinct. Yet even these ex- 

 amples of insect behavior have one point in common ; they are started 

 by some simple stimulus, and once set going, they invariably are 

 carried out to the same conclusion, regardless of circumstances. Thus, 

 a female codling moth, the parent of the common worm found in 

 apples, frequently lays its eggs on the leaves of trees which are bear- 

 ing no fruit, with the inevitable result that all its offspring die. 



Rarely, in the highly specialized orders, such as the bees or ants, 

 insects are observed to follow a procedure that seems to demand 

 some reasoning power as its basis. An indi\'idual apparently will 

 learn by experience, and voluntarily modify its procedure in going 

 through a similar action. Such cases, however, are not common. 

 Most insect behavior is automatic and purely reflex. 



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