FISH ENEMIES 147 



cent passersby who, for their unwariness, will pay with their lives. 

 Water scorpions depend upon their obscurity to get near their prey, 



Fig. 142. Water Scorpion (Life size) 



which they quickly seize with their modified forelegs. While this 

 insect is common enough to the naturalist, it is not one with which 

 the fish-culturist need be seriously concerned. 



Whirligig Beetle (Gyrinidce). This well-known beetle is common 

 to many slow-flowing streams and pools, keeping up a perpetual 

 movement on the surface of the water, on which it glides apparently 



Figs. 143 and 144. Whirligig Beetle and Larva (Enlarged three times) 



without effort. On account of its size and shape it is often called the 

 coffee bug. The breeder of fishes is not harassed by this insect, but 

 occasionally an aquarist will be tempted to introduce one in a fish- 

 tank. This is a mistake. They are predaceous and can inflict a severe 

 bite. The larva, which is not so well known, is also predaceous. This 

 little beetle when held in the hand emits a faint but pleasant odor. 



Water Strider (Hydrometridce). Another of the predaceous 

 aquatic insects is the Water Strider. Quite as well known as the 



Fig. 145. Water Strider (Life size) 



Whirligig Beetle, it adopts somewhat the same methods of securing 

 its prey, darting over the surface of the water, waiting for the stream 

 to bring down some helpless insect victim that has fallen overboard. 

 They are capable of catching young fishes which come to the surface. 



