134 LIVING FISHFOODS 



usual effects of being overfed. A certain degree of care must be 

 exercised not to place so much daphnia into the aquarium as to suf- 

 focate the fish. Daphnia breathe the free oxygen in water the 

 same as do fish and therefore too many will soon exhaust oxygen 

 from water. The fish will die of suffocation sooner than the daphnia. 

 Many beginners have lost fish in this way. A good practice is to give 

 the fish all they can eat in about a quarter of an hour and still leave 

 some few daphnia swimming about. 



124 125 



Fig. 122. Daphnia (Greatly enlarged) 



Fig. 123 



Mosquito Larva (Greatly enlarged) 



Egg Raft and Individual Eggs (Greatly enlarged) 



Pupa Before Transforming to Mosquito (Greatly enlarged) 



Fig. 124. Cyclops (Greatly enlarged) 



Fig. 125. Cypeis (Greatly enlarged) 



A popular name for daphnia is "ditch fleas." This will give a hint 

 as to their appearance, as they are approximately the size and shape of a 

 flea, except that they have two rather long, branched swimming arms 

 which are always in motion and which give the animal a sort of hopping 

 motion through the water. Without this perpetual swimming the daphnia 

 would sink to the bottom, as they are heavier than water and have no 

 air bladder. A greatly magnified illustration is shown in Fig. 83. 



Daphnia (pronounced "daft'ney" in the vernacular) are known 

 among fish breeders as "insects," but they are really not such, being per- 

 fect freshwater crustaceans as much as a crayfish. The shell, though 

 soft, contains mineral elements which are very desirable, while the flesh 

 itself is easily digested and nutritious. This little creature is found in 

 freshwater nearly all over the world, principally in still pools where there 

 are no fish. For the practical purpose of catching daphnia in sufficient 

 quantities to feed fish the collector should hunt pools in which there is 

 considerable animal or vegetable decomposition in process. Such condi- 

 tions are found to perfection in the pools on the ground where city refuse 

 is dumped. When the conditions are favorable the daphnia rise to the 

 surface in such quantities as to color the water, the usual color being a 



