78 HOW ARE ANIMALS AND PLANTS DEPENDENT? 



they live becomes overcrowded and the food supply runs short. 

 Then a generation of winged aphids is produced. These fly away 



y jgrovnd. on 

 ~ Sap from roots 



Life history of the seventeen-year cicada. What are the chief differences 

 between this life history and the others shown ? 



to other plants, and reproduction goes on as before until the 

 approach of cold weather, when males and females appear. Ferti- 

 lized eggs are then produced which give rise to young the following 

 season. 



Dragon flies and their relatives. The dragon fly receives its 

 name from the fact that it preys on insects. The adult eats 

 mosquitoes and other insects which it captures while flying. Its 

 four large, lacelike wings give it power of very rapid flight, while 

 its long, narrow body is admirably adapted for the same purpose. 

 The large compound eyes placed at the sides of the head give 

 keen sight. It possesses powerful jaws (almost covered by the 

 upper and lower lips). 



These insects deposit their eggs in the water, and the fact that 

 they may be often seen with the end of the abdomen curved down 



