CH Arad kK oC] 
INSECT BEHAVIOR 
The subject of insect behavior will be considered under three 
heads: (1) Tropisms, (2) Instinct, (3) Intelligence. 
1. TROPISMS 
Environmental influences, such as light, temperature or 
moisture, may control the direction of locomotion of an organ- 
ism by determining the orientation of its body. The reaction 
of the organism under these circumstances is known as a 
tropic, or tactic, reaction. A moth, for example, flies toward 
a flame—is positively phototropic; a cockroach, on the con- 
trary, avoids the light—is negatively phototropic. A plant 
turns toward the sun—in other words, is positively helio- 
tropic. 
An insect flies toward the light as inevitably and as mechan- 
ically as a plant turns toward the sun; indeed, the two phenom- 
ena are fundamentally the same. Some students, however, 
prefer to use the term taxis for bodily movements of motile 
organisms, and the term tropism for turning movements of 
fixed organisms. 
The study of tropic reactions, though comparatively new, 
has already illuminated the whole subject of the behavior of 
organisms and placed it on a rational basis. ‘The complex 
tropisms of insects offer a fresh and large field to the investi- 
gator, comparatively little having as yet been published upon 
the subject. 
Chemotropism.— Positive and negative chemotropism, as 
Wheeler observes, ‘are among the most potent factors in the 
lives of insects.” Insects are affected positively or negatively 
by such substances as can affect their end-organs of smell or 
taste. Positive chemotropism enables many insects to find 
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