280 Modern Fishcultiire in Fresh and Salt Water. 



yearling trout. It has swimming legs behind, power- 

 ful forelegs, a boat-shaped body and a sharp probos- 

 cis; the larva of this beetle is a green worm the size of 

 a lead pencil and nearly three inches long. Always kill 

 these things. The margined beetle (Dytiscus) has hard 

 shards covering the wings, strong swimming legs, and 

 a pair of pincers in front; length of body one and one- 

 half inches; female with fluted shards and male with 

 smooth shell-like back, around which runs a yellowish- 

 white stripe; the larva is the ''water-scorpion/' a round- 

 bodied larva, with light rings at each abdominal joint. 



PUPA OF DRAGON FLY (natural size). 



The larva and pupa of the dragon-fly are very destruct- 

 ive to small fish. Few insect pupa take food, but this 

 animal feeds all the time; it has a pair of pincers on an 

 extension arrangement, which is hinged to the front 

 part of its head; there is a middle joint to this which 

 lets the pincers lie in front when in repose, but allows 

 them to be thrust out nearly three-fourths of an inch 

 when it seizes a fish. I once put six young gold-fish, 

 three-quarters of an inch in length, in a bowl with a 

 dragon-fly larva, and it killed all six fish inside of an 



