THE STRUGGLE FOR EXISTENCE 



357 



of the ^\dngs are dark, with purple and orange markings, 

 so that when flying, the butterfly is quite conspicuous. 



Then, again, there are the small green snakes that live 

 in the grass; the earth-colored snakes that live along the 

 bare roadsides or in 

 bare fields; the tree 

 frogs that have gro\^n 

 to imitate the bark 

 of the trees on \\'hich 

 they live or, if they 

 live among the leaves, 

 then have grown to 

 resenil3le the leaves 

 in color. 



A very interesting 

 and remarkal^le case 

 of protective resem- 

 blance is seen among 

 those animals in ^^'hich 

 there is an actual 

 change of color of their fm- coats to correspond to the 

 season. The American hare (calletl the white rabbit) in 

 summer is of a cinnamon brown; but, as winter comes 

 on, its coat turns to a «'liite color. 



Again, certain spiders that live in flowers are colored like 

 the flowers, so that they remain hidden and lie in wait to 

 catch their prey of unsusjjecting insects that visit such 

 flowers for nectar. Such resemblances are known as ag- 

 gresf:'ive resemblances. 



Mimicry. — In the struggle for existence, the weaker or 

 more vulncralde animal often happens to vary in such a 

 manner that it resembles a stronger or UKjre aggressive 



Fig. 236. — Kalliina. 



