Dec, 1921 FOOD of oitio darters 57 



somewhat. There is a tendency also to omit entomostraca from 

 the food of infancy and to take larger insect larvae at once. 

 E. cceruleum resembles the more generalized darters in this 

 regard, having a large proportion of copepods up to the 15 mm. 

 stage. 



The length of the fish has been taken to indicate its age 

 throughout this discussion but it is recognized that the rela- 

 tionship is only relative, especially when comparing members 

 of different species. Thus it appears that E. flabellare has 

 passed into the stage of youth by the time that it has gained a 

 length of 10 mm. but Percina caprodes does not pass into this 

 stage as indicated by its food habits till it reaches a length of 

 25 mm. After studying P. caprodes, therefore, one is likely to 

 fall into the error of considering the much smaller specimens of 

 E. flabellare as correspondingly younger. Indeed, it may be an 

 error in this paper to have stated that the stage of infancy in 

 Etheostoma is poorly represented, for it is possible that specimens 

 may be found which are less than 10 mm. in length and which 

 eat entomostracan food. 



Summary of Comparison of Food Habits. 



The darters may be divided roughly into three classes based 

 upon the character of the food at the different periods in their 

 lives. First : a group with generalized food habits such as those 

 found in the perch and the sunfishes. In this class three periods 

 are to be recognized in the life of an individual ; infancy, when 

 the food consists of entomostraca and minute midge larvae, 

 youth, in which may fly larvae, small midge larvae and small 

 amphipods form the food, and maturity during which period 

 the food is varied and is likely to contain a large proportion of 

 large insect larvae, large amphipods and snails. Second: one in 

 which the period of youth is shortened or omitted and the 

 adults subsist to a considerable extent upon vegetation and 

 debris. Third: a group of miniature game fishes which begin 

 at a very early stage to hunt for large may fly larv«, midges and 

 other active larvae. The period of infancy is curtailed so much 

 as to seem entirely absent or is merged with youth. The habit 

 of taking large food animals continues to the adult stages and 

 the habit is accompanied by an unwillingness to take either 

 debris or vegetation. 



