FISH ENEMIES 145 



ing a vicious, pincer-like organ called the "mask," rarely missing the 

 object of attack. The method of propulsion through the water is 

 peculiar, being brought about by a series of expulsions of water from 

 the hinder end. This enables them to make a very sudden leap 

 towards a victim. The "mask," shown in Figure 137, when not in use 

 is folded before and under the head. Dragon Fly larvae are strictly 

 carnivqrous at all periods and will attack any pond creature reason- 

 ably near its own size. If given enough time a single individual will 

 destroy an entire hatching of fishes, growing by what it feeds upon 

 so as to be able to devour the remaining fishes which are also becom- 

 ing larger. 



Predaceous Diving Beetle (Dytiscus). Fortunately this beetle is of 

 such size that it can scarcely escape notice, especially as it is obliged 

 to come to the surface for air, which it takes at the end of the abdo- 

 men. It is rapacious in extreme degree and is a good swimmer. A 



Fig. 138. Predaceous Diving Beetle (Life size) 



large specimen was once placed in an aquarium for observation. It su 

 quickly attacked a goldfish that the scales fell in a small shower and 

 the fish died before it could be rescued. The males may be distin- 

 guished by the ball-like development on the forelegs. They are 

 usually of such a dark brov/n as to appear black, but are sometimes 

 marked or bordered with yellow. 



Water Scavenger Beetle (HydrophilidceJ. We mention this beetle 

 here because of its resemblance to the large predaceous diving beetle. 

 It swims dift'erently, using its legs alternately, while the diving beetle 

 moves opposite pairs together. The Scavenger Beetle is also dififerent 

 in that it breathes at the surface from the mouth. Instead of long 

 antenns, they have palpi looking like club-shaped antennae. This 

 beetle lives chiefly on decomposing vegetal and animal matter, 

 although taking soft living plants such as Nitella. It has been claimed 

 to be predaceous, but there is doubt about their attacking fishes. 



