100 



FISH ENEMIES 



Water Scorpion (Neptidce). We have here another of the insects 

 spending most of its time in aquatic dirt and rubbish awaiting innocent 



Fig. 80. Water Scorpion (Life size) 



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

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

 the fish-culturist need be seriously concerned. 



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

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

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



Figs. 81 and 82. Whirligig Beetle and Larva (Enlarged three times) 



which is not so well known, is also predaceous. This little beetle when 

 held in the hand emits a faint but pleasant odor. 



Fig. 83. Water Boatman (Slightly enlarged) 



Water Boatmen and Back Swimmers (Corixidx and Notonectida) 

 are found everywhere in still or slow-moving water. There is a wide 

 variation of opinion as to the predaceous characteristics of these insects. 

 This is because fish breeders ordinarily class them all as "boatmen," a 

 very natural mistake owing to their general resemblance. The facts are 

 that Back Swimmers (fortunately much the fewer in numbers) are carniv- 

 orous, predaceous and capable of inflicting a severe bite when being 

 handled. They are fish enemies. Water Boatmen are harmless scav- 

 engers. In swimming they use their longest pair of legs like oars, which 

 accounts for their name. 



