218 Phylum Art hr op oda 



Midges of the genus Chironomus are attracted to the pond within a 

 day or so after adding fertilizer, probably by the odors of fermentation, 

 and deposit enormous numbers of eggs. These add considerably to the 

 production of the pond. Mosquitoes likewise are attracted at about the 

 same time and their characteristic floating egg masses become con- 

 spicuous all over the surface. 



These three associated organisms may be considered beneficial insofar 

 as they increase considerably the production of fish food. The mosqui- 

 toes, however, are obnoxious as adults and since they transform to the 

 adult stage long before the Daphnia culture reaches a peak, it is prob- 

 ably better to exterminate them with non-toxic oil spray 4 to 6 days after 

 the eggs appear. Other groups of animals which almost invariably appear 

 are the back-swimmers, larvae of aquatic beetles, nymphs of dragonflies 

 and damselflies, and hydra. All are predatory on Daphnia and midges. 

 It is well known that the oil spray kills all insects that must come to the 

 surface for air, such as the larvae of mosquitoes, beetles and adult back- 

 swimmers. The dragonfly and damselfly nymphs and hydras are elimi- 

 nated when the pond is drained and disinfected. 



Table I. 



Amount of Fertilizer per 100 Cubic Feet of Water and Its Apportionment 

 (Experimental Ponds at Ithaca, N. Y.) 



Sheep Manure 

 Soy Bean Cotton Seed Dry and 



Fertilizer Meal Meal Buttermilk Soy Bean Meal 



Many different fertilizers have been tried, including manure from 

 horses and cattle, dried sheep manure, acid phosphate, soy bean meal, 

 cotton seed meal, dry buttermilk, and alfalfa meal. The alfalfa meal pro- 

 duced only fair cultures and required such a large quantity of material 

 that experiments were early discontinued. The dried sheep manure used 

 in combination with either acid phosphate or soy bean meal produced 

 average cultures consistently. The wet animal manures were from ordi- 

 nary barnyard piles containing much straw and slightly rotted. The re- 

 sulting cultures were about average but not always dependable. The 

 fertilizers which gave cultures averaging the highest were dry buttermilk, 

 soy bean meal, and cotton seed meal. Very little difference between them 

 was noted. 



