BULIvETiN OF THE BUREAU OF FISHERIES. 



held as a most important responsibility of the station to stimulate and to guide the 

 development of fish farming as a more widespread industry. This function as a fish- 

 cultural experiment station should rightly be regarded as second to none." 



On page 398 of the same report he stated: "It is manifest that the assembly of 

 fish-cultural ponds, supplied originally with water from the Mississippi, but permitted 

 to develop essentially pond conditions, stocked with abundant aquatic vegetation 

 and rich in entomostraca, insect adults, and larvae, together with the customary variety 

 of smaller animal forms that thrive on the bottom, amidst the vegetation or in free- 

 swimming condition, offer favorable opportunities for biological and physiological 

 studies bearing upon problems of fish food, as well as for investigations of more par- 

 ticular scientific interest." 



One feature of the environment, especially well developed at Fairport, and which 

 will always be present in the pond culture of food fishes, is the presence of a greater 

 or less number of dragonflies and damselflies which pass their larval life in the waters 

 of the ponds and their adult life in the immediate vicinity. It becomes, therefore, of 

 considerable importance to know whether the presence of these larvae and adults is 

 beneficial or injurious to the fishes. The ecology of this problem forms the main theme 

 of the present paper, to which is added a list of such species as have been obtained 

 at or near the station during three years of collecting. 



The observations here recorded were made during the months of July and August, 

 together with the last week in June and the first week in September. Some species 

 emerge earlier in the year, but they usually have a second period of emergence within 

 the limits just mentioned, and hence it is believed that the present observations cover 

 all species of real importance. 



GENERAL DESCRIPTION OF THE PONDS AND THEIR ENVIRONMENT. 



The position and arrangement of the ponds of the Fairport station are clearly 

 shown in the accompanying map. For convenience of manipulation they have been 

 divided into six series called, respectively, A, B, C, D, K, and F, the ponds in each 

 series being numbered independently. Series A and C are small cement ponds or out- 

 of-doors aquaria for the temporary keeping of fish and mussels under experimentation 

 and do not concern the present discussion at all. Series B and F are dirt ponds filled 

 for the first time in July, 191 6, and used the remainder of that summer and ever since. 

 But owing to their newness when the present investigation on dragonflies and damsel- 

 flies was begun, they were given no attention. During the summer of 191 7, however, 

 some of the observations on the food of odonate imagos were made around the shores 

 of these ponds. Some of the young fishes also, the food contents of whose stomachs 

 were examined during 191 7, came from these ponds. This leaves only series B and D, 

 the former south of the railroad and within 200 feet of the river bank, the latter north 

 of the railroad and much farther from the river. Series B is made up of six small 

 dirt ponds, the largest only 0.19 of an acre in extent, all of them heavily filled with alga 

 and water vegetation of various kinds. 



Series D, on the other hand, contains nine large ponds with a total area of nearly 

 6 acres and presents admirable conditions for an ecological study of their environment. 

 This is the series upon which the present study is based; they are all dirt ponds of the 

 usual construction, having wide embankments thickly covered with vegetation, and , 



