CHAPTER V 
Tue Benavior 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 light; 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 individual 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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