400 APPLIED BIOLOGY 



colors are commonly interpreted as (1) protective, (2) ag- 

 gressive, (3) warning, (4) mimicry. 



(1) Protective coloration is the most common form of 

 useful colors among insects. A green insect on a green leaf is 

 more or less concealed because it so closely resembles its 

 surroundings. Many insects resemble the bark of trees 

 on which they rest, and some both in form and color resemble 

 sticks and leaves. In still other ways numerous insects 

 resemble the objects near which they habitually live. Such 

 similarity to the environment is believed to be protective 

 against enemies. Note that it is not absolutely protective, 

 for such insects are often captured by birds; but probably 

 more such insects escape than would if they were not pro- 

 tectively colored. 



(2) Aggressive coloration is the term applied to insects 

 which resemble their environment so that they can lie con- 

 cealed from their approaching prey. This is found in certain 

 predaceous insects like the mantis, which at the same time 

 are protectively concealed from such enemies as birds. 



(3) Warning Coloration. Many insects are conspicuously 

 colored, and appear to make no attempt at hiding themselves. 

 The common monarch butterfly is an example. The ex- 

 planation is that such insects often have a disagreeable odor, 

 flavor, or sting which repels their enemies; and hence the 

 conspicuous color is a danger signal. 



It has been learned by experiments that insect-eating 

 monkeys soon learn that such a conspicuous coloration is 

 associated with disagreeable things and thereafter will not 

 attempt to catch such insects. This suggests that a species 

 with warning colors would have an advantage in that the 

 comparatively few individuals caught might teach the enemy 

 that such brightly colored insects are not good to eat. It 

 is probable that very many cases of conspicuous coloration 

 in insects are of value as warning colors. 



(4) Mimicry. This means the resemblance of one 



