104 



Aquatic ILitt 



ously on Daphnia and mosquito larvae, 

 and materially deplete the supply if per- 

 mitted to remain. Most enemies can be 

 sifted out under water through a tea 

 strainer or flour sieve. 



A consideration is usually overlooked 

 that is probably worth thought. That is, 

 the water in which the Daphnia are kept. 

 The common practice is to place them in 

 clean, fresh water. This would seem to 



be crystal clear, and many young Daphnia 

 will be observed. 



Cypris or "hard-shell daphnia" are not 

 quite such good food, but make an accept- 

 able second choice. They are extremely 

 hardy, and may be bred in large numbers 

 by supplying them with decaying leaves, 

 etc. They will stand heat and extreme 

 crowding. 



Mosquito larvae, on the other hand, 





I 



Scrimshaw Working a Florida Pond 





be a mistake unless they are intended for 

 immediate use. The water of the ponds 

 in which they occur naturally is well 

 charged with the food they require. To 

 rob them of this entirely is to weaken 

 them and shorten their lives. It is better 

 to use the same water, but dilute it. If 

 green aquarium water can be had it is 

 better than clear water, the microscopic 

 vegetal organisms being perfectly good 

 for Daphnia. This can be well demon- 

 strated by removing fishes from a green- 

 water aquarium and introducing a supply 

 of Daphnia. In a few days the water will 



should not be allowed to feed. In clear 

 water their development is retarded, par- 

 ticularly if kept cool. However, when 

 they have developed to a good size it is 

 impossible to prevent their turning into 

 fully developed mosquitoes. A good plan 

 to prevent the escape of mature indi- 

 viduals is to keep the larval stock in a 

 large bottle, partially filled with water, 

 inverting it to pour out larvae desired for 

 feeding. After the bottle is emptied, the 

 hatched mosquitoes may be drowned by 

 filling the bottle with water, pouring it 

 through mosquito netting fastened over 

 the mouth. 



