200 



BULIyETiN OF THE BUREAU OI? FISHERIES. 



but the teeth are either completely lost, as in the dragonflies and in Lestes among the 

 damselflies, or they are reduced to a much simpler form. The imago evidently chews 

 its food before swallowing it, as we may well believe after watching one munch its prey. 



This brief description of the mouth parts of the nymphs and imagos will enable us to 

 understand better both how they secure their prey and how they dispose of it afterwards. 



ECONOMIC RELATIONS BETWEEN ODONATES AND FISHES. 



The artificial propagation of fish falls very naturally into three great divisions: 

 I. Suitable methods of obtaining and hatching the eggs; 2. Care and protection of the 

 young after they are hatched; 3. Provision of an abundance of the right kind of food. 



Our national and State fish hatcheries are concerned very largely with the first two 

 of these, and the progress they have achieved is marvelous, considering the difficulties 

 surmounted. In a comparatively brief period of years they have accumulated a wealth 

 of accurate information and statistics, which have attracted the attention and awakened 

 the admiration of the entire world. 



But the last factor, in so far as it concerns pond fishes, has thus far received 

 almost no attention in this country. Europe has been studying the problems connected 

 with fishponds for many years and has far outstripped us along these lines. In fact, we 

 have made hardly a beginning as yet, and the few facts that have been ascertained still 

 lack correlation and logical arrangement. 



In speaking of the food relations of insects and fishes Needham (1901, p. 395) said: 

 "And so little are the essential features of good foraging ground understood that each 

 planting of fry in a new place is still largely an experiment. * * * Any new study 

 of fish food should include the study of the feeding grounds, feeding habits, choice of 

 food offered, and conditions that make for the continuance and possible increase of the 

 food supply." In spite of the 15 years that have elapsed since then, the statement 

 retains practically its full value to-day. 



Prof. S. A. Forbes and his associates in Illinois were pioneers in this aspect of fish 

 culture, and have put out much valuable information on the food of fresh- water fishes 

 during the last 35 years; an admirable summary will be found in Forbes, 18886. More 

 recently papers have been published by L. L. Dyche, 1914; Wm. B. Meehan, 191 3; A. S. 

 Pearse, 1915; Geo. C. Embody, 1915, and Dr. Robert E. Coker, 1915. 



These papers are all excellent in both their subject and its treatment, but of 

 necessity they are general in character and do not treat any of the phases in detail. 

 For this reason and for many others it is believed that a summary of the economic 

 relations between odonates and fishes will prove of interest to all who are, and 

 especially to those who may become, engaged in pondfish culture. At present the old 

 idea prevails that the nymphs of the Odonata, especially those of Anax, ^Eschna, and 

 other large species, are very destructive to small fishes. 



So far as known, the other side of the question has never been presented, and we 

 have not only drawn a one-sided and biased conclusion, but we have also been led 

 into the common error of condemning the many for the sins of the few. A hawk steals 

 a farmer's chicken, and immediately all hawks are condemned as pests and robbers, 

 irrespective of species, and a loaded shotgun is kept for their reception. Similarly 

 because Anax and ^Eschna nymphs have been known to kill small fish, all dragonfly 

 nymphs have been condemned as nuisances and dangerous to have around a fishpond. 



