THE STRUGGLE FOE EXISTENCE 



355 



enemies. In other words, animals are constantly being 

 changed, or adapted, to meet their surrounding conditions; 

 and those best adapted to their environment are most apt 

 to survive. 



Resemblances. — No matter how closely we watch the 

 Carolina locust in its flight along a dusty roatl,we shall have 

 great difficulty in fintling it after 

 it alights, because the color of its 

 wings so closely resembles that 

 of the dust. Again , we shall have 

 difficulty in finding bobwhite in 

 the grass or among the weeds, 

 no matter how carefully we 

 follow his song, because his color 

 blends so nicely with the sur- 

 roundings. Such resemblances 

 enable these animals to escape 

 their enemies and are, therefore, 

 known as protective resemhlances. 

 The insects are especially notable 

 for their many examples of such 

 resemblances. 



An excellent instance of such 

 a resemblance is foimd in the 

 case of the katydid. In this 

 insect the wings resemble leaves 

 so closely in color and appearance as to deceive the 

 most observant. In fact, all katydids have A\ings that re- 

 semble leaves more or less in appearance. Those insects 

 familiarly known as walking sticks are \'^ry easily mistaken 

 for the branches of the trees on which they live. Some 

 have irregular outgrowths on the body and limbs which 



Fig. 234. — Walking .stick in- 

 sect with projections on its 

 body and legs like those on a 

 rougli branch. 



