THE ARTHROPODS 401 



species of insect to another which has warning colors. The 

 American viceroy butterfly is a mimic of the monarch. 

 Young insect-eating monkeys will eat viceroy butterflies, 

 but will not touch them if they have first tasted some un- 

 palatable monarchs. This leads to the view that the viceroy 

 species gains decidedly by resembling and thus living on the 

 bad reputation of the monarch, which has warning colors. 

 In tropical countries there are numerous similar cases where 

 a conspicuous insect which has no special defense against 

 its enemies is similar in appearance to another species whose 

 conspicuous colors are warning signals, advertising boldly to 

 enemies that there is danger. 



The word " mimicry " suggests conscious imitation ; but, 

 of course, one insect resembles another because it happened 

 to be developed that way. We do not know how the first 

 viceroys came to resemble monarch butterflies, but probably 

 a butterfly appeared which was unlike its near relatives 

 and more like monarchs. This resemblance to the monarchs 

 gave the first viceroy an advantage. Other viceroys de- 

 veloped because " like tends to produce like," which principle 

 of embryology applies especially to the propagation of indi- 

 vidual organisms born with some peculiarity. Obviously, 

 any slight advantage gained by the resemblance to the mon- 

 archs, which are not so liable to attack as are more edible 

 insects, would have tended towards the continued multi- 

 plication of viceroys. It is thus easy to suggest how viceroys 

 might have been preserved and allowed to multiply; 

 but it has not yet been discovered why the first viceroy hap- 

 pened to be so unlike its relatives. 



The above explanation of insect colors as protective, 

 aggressive, warning, and mimicry is believed to apply to 

 many insects. It should be understood that these devices 

 for use of colors are not absolutely perfect in their working. 

 For example, green grasshoppers concealed in green leaves are 

 often discovered by birds ; but there is reason to believe 

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