POND LIFE. 125 



5. Study the legs and observe that the fore and 

 middle legs are furnished with claws, and are fitted 

 for clinging to plants and stones and for seizing prey, 

 while the hind legs are destitute of claws and are 

 fitted for swimming. Make a drawing of one of the 

 hind legs, also one of a fore or middle leg. 



6. Study the wings. These are closely folded 

 over the back of the abdomen. The fore wings are 

 thick and heavy at the base, while the tips are thinner 

 and overlap. This type of wing is found only in the 

 order Hemiptera or bugs. Carefully spread the fore 

 wings apart with a pin and observe the hind wings, 

 which are beneath them ; these are very thin and 

 transparent ; they are stiffened by a few stout veins, 

 and are folded lengthwise on the back of the abdo- 

 men ; in a recently killed specimen they can be 

 spread with a pin. Like most other pond insects 

 that we have studied, the back-swimmers can leave 

 the water and fly to some other pond if they do not 

 like their surroundings. They do not have this free- 

 dom, however, until they are grown up. Early in 

 the summer back-swimmers are found that have no 

 wings; these are the young ones, the nymphs, on 

 which the wings have not yet grown. If you have 

 wingless specimens in your collection, label them 

 Nymphs. 



7. Study the belly side of the abdomen. Along 

 the middle line there is a prominent ridge which is 

 thickly clothed with hairs, and, on each side between 

 this ridge and the edge of the body there is a deep 

 furrow. Along the upper edge of the outside of this 

 furrow, and a short distance from the side of the 

 body, there is a fringe of long hairs. Wet a pin and 



