72 ANIMAL BIOLOGY 



sluggish stealthy prowling of the other in the bottom of 

 a pond and stream. 



The damsel flies have a slender body, broad head with 

 widely separated eyes, and very delicate wings which are 

 held longitudinally over the abdomen when at rest. The 

 damsel flies are frequently conspicuous on account of their 

 beautiful coloration, and they are generally found flit- 

 ting about near the water. The larvae usually have long 

 flattened appendages at the end of the body called tracheal 

 gills which are abundantly supplied with tracheal tubes 

 for carrying air which is absorbed from the water. 



The larvae of the May flies resemble in many ways those 

 of the dragon flies, but they may usually be distinguished 

 by a number of tracheal gills attached 

 to the sides of the abdomen, and by 

 the long thread-like feelers at the end 

 of the body. The gills are kept mov- 

 ing back and forth, thus keeping the 

 water near them in constant circula- 

 tion. The larvae of some species of 

 May flies live in the water for two, or 



skin many times, their wing buds be- 

 coming larger with successive molts. Finally they come 

 to the surface, and the winged insect emerges from the 

 nymphal skin. This process may occur when the larvae 

 is lying at the surface of the water, the old skin serving 

 as a sort of raft or float which keeps the winged insect 

 from getting wet. The life of the mature May fly is 

 very short, some forms living but one or two days, 

 hence the term Ephemeridae which has reference to the 

 ephemeral existence of the members of this family. Soon 

 after the insects emerge they cast a very delicate skin, 

 mate, and then lay their eggs in the water. They take 



