84 ARTHROPODS 



organs are their weapons of defense. The following are 

 some of the things against which they continually struggle : 



(i) Enemies. — Every insect is surrounded by myriads 

 of hungry aggressive foes which it must combat or elude if 

 it lives. 



To do this some animals have modified mouth parts for 

 fighting ; others, hard shells ; others, wings for sudden and 

 rapid flight; others, legs developed for leaping; others, 

 glands for emitting an offensive odor ; others, a sting ; 

 others adopt the color of some article, as leaf, bark or stone, 

 which is not food for their enemies ; others imitate the color 

 of an animal which is not relished by their enemies ; others 

 burrow into the ground ; while many have compound eyes, 

 by means of which they detect the approach of an enemy in 

 time to escape. This vigilance applies in some cases not to 

 the insects themselves only, but is. exercised toward the off- 

 spring, by placing the eggs in protected places, and by de- 

 fending the young in all stages from attack. 



(2) Food Supply. — The food problem is an important 

 one and every insect is well prepared to get some certain 

 food in a certain way. Some have mouth parts for tearing 

 or masticating dead or living prey; others, for sucking 

 blood or sap ; others, for getting nectar from flowers ; 

 others, for using the pollen of flowers ; others, for biting 

 or masticating the entire leaf ; others, for boring into woody 

 stems or roots and devouring them ; others, for penetrating 

 grain ; others, for rasping and absorbing liquid ; others for 

 living on decayed vegetable matter, while some do not have 

 mouth parts in the mature state and hence live without food 

 until they die of starvation or accident. 



In nearly all of these the food is obtained bv the mouth 



