90 AGRICULTURAL EXPERIMENT STATION. 



swimmers (Notonecta) and water-boatmen are common, wrig- 

 lers are scarce. These insects are usually plentiful where the 

 duck-weed occurs and help to clear those parts of the ponds 

 which the plant does not cover. 



The water striders or skaters get all their food on the surface 

 and I have never seen Anopheles larvae where these insects oc- 

 curred in numbers. 



The water scorpions (Nepa and Ranatra) are curious bugs 

 with either a narrow or a very flattened body and long slender 

 legs. They live in the shallow water at the edges of quiet ponds 

 and get their air supply through a slender tube that they extend 

 to the surface of the water. They therefore walk around on the 



Figure 23. 



A Water-scorpion, Ranatra fusca. (Re-drawn from Coinstock.) 



bottom with the long middle and hind legs, but keep in touch with 

 the outer air by means of this breathing tube. The fore-legs are 

 developed into a pair of grasping organs with which they capture 

 their prey and bring it within reach of the short, sharp-pointed 

 beak. Mr. Viereck comments on these insects as follows : 



"The early stages of Ranatra fusca were destructive to wrig- 



