DRAGONFIvlES AND DAMSELFUES IN PONDFISH CULTURE. 2ig 



of egg layers around the ponds, and thus affects the supply of fish food. Would it not 

 be better to get rid of the dragonflies and allow these other insects to breed without 

 hindrance? At first sight it seems as if the answer must be in the affirmative, but a 

 little reflection makes it appear differently. If the nymphs of the dragonflies make as 

 good food for the larger fish as the larvae of these other insects make for the smaller 

 fish, then it is as important for the dragonfly imago to survive and lay its eggs as for 

 any of these other species. Larger fish will not thrive well on food suitable for fry, and 

 if something is not provided for them they will eat one another. Bass, perch, sunfish, 

 buffalofish, catfish, and crappies are well satisfied with the larvae of mosquitoes, gnats, 

 and flies for a while and will thrive on them. But the time soon comes when this food 

 no longer satisfies them and they demand something larger. (See p. 225.) 



The period during which the smaller larvae prove sufficient varies considerably 

 with the kind of fish, but they will all thrive better if the larger food is present in the 

 pond, so that they can change to it gradually whenever they choose. It is definitely shown 

 in another place (p. 228) that when the young fish reaches a length of about 25 mm. it 

 begins to eat odonate nymphs. It takes some fish much longer to reach this length 

 than it does others, and even in the same brood some fish grow faster than others. 

 Hence the larger food must be present all the time to accommodate the different rates 

 of growth. 



Furthermore, actual observation shows that the presence of odonate nymphs and 

 imagos does not necessarily diminish the supply of smaller fish food. The number of 

 dragonflies has steadily increased around the Fairport ponds during the last five years, 

 but at the same time the number of other insect larvae and Entomostraca has increased 

 apparently as much, so that conditions suitable for fish culture were never better than 

 at the present time. 



Again, whatever the kinds of fish, they must be successfully carried through the 

 winter, and there must be enough food in the pond to keep them in good condition. 

 By the time the pond freezes over most of the young fish have become large enough to 

 demand good-sized food, and the larger they grow the more insistent will this demand 

 become. Moreover, some of the animals which are included among this smaller food, 

 such as the Entomostraca and several of the insect larvae, are much less numerous 

 during the winter. At other times of the year odonate nymphs furnish acceptable food 

 for fish, and there is every reason to believe that they continue to do this through the 

 winter, which is just the season when it is most needed. Only a few fish have been 

 examined at Fairport during the winter, but the limited observations that have been 

 made seem to support this idea. Twelve largemouth black bass, Micropterus salmoides, 

 averaging 130 mm. in length and 18 bluegills, Lepomis incisor, averaging 107 mm. in 

 length, from pond iD, 19 of the same bass, 44 mm. in length, from pond 2D, and 12 

 bass, 185 mm. in length, from pond 3D, were examined February 15-17, 1917. Of 

 these 61 fish, the stomachs of 46 were found to be either entirely empty or so near it 

 that the debris present was indistinguishable. The food of four of the remaining 

 fish, two bass and two bluegills, consisted entirely of odonate nymphs, and they were 

 probably identified in the debris of the stomachs of two other bluegills. This record 

 is too meager to possess much value beside the ample proof elsewhere presented (p. 225), 

 but it does show that the fish will eat nymphs during the winter, as suggested. 



As a third consideration, although nature's equilibrium must be made subservient 

 to man's designs and control in intensive pondfish culture, it is still true that, other 



