WATER BEETLES IN RELATION TO PONDFISH CULTURE. 



255 



Ephemerida, and the Odonata and Coleoptera were tied for third place. Pearse 

 divided the fish foods into nine classes, the first four of which in the order of their 

 importance were: (1) Insect larvae, oligochaetes, and leeches. (2) Entomostraca. 

 (3) Fishes and frogs. (4) Insect pupae and adults. In the present instance the 

 larvae and adults are combined in one table, while the pupae, transforming out of 

 water, are never eaten by fish. This beetle food, therefore, belongs partly to the 

 class considered of greatest importance and partly to the class placed fourth in 

 the list. 



Pearse's table may well supplement the preceding one, since it includes several 

 kinds of fish not mentioned by Forbes and also adds new items to the diet of other 

 species. Of greatest interest is the inclusion of the German carp, of which 40 

 young specimens, varying from 15 to 64 mm., were examined. These had eaten 

 freely of gyrinid larvae, haliplid adults and larvae, dytiscid adults and larvae, and 

 hydrophilid larvae, the sum total forming an amount of food surpassed only by the 

 Diptera and Entomostraca. Pearse said (1918, p. 258) : 



The German carp during its first few weeks after hatching from the egg feeds largely on entomostra- 

 cans and rotifers; after that it turns more to insect larvae. 



And of this insect food the beetles are second in importance. 



It is also worthy of note that three young suckers, averaging 2 inches in 

 length, had consumed enough dytiscid adults to form a respectable percentage of 

 their total food. The little Iowa darter subsists almost entirely upon amphipods 

 and insect larvae, and among the latter the beetles are second only to the Diptera. 



The only family of aquatic beetles not found in the food of the bluegill as 

 given by Forbes was the Haliplidae. All of the 25 specimens of bluegill examined 

 by Pearse contained haliplid larvae, the larger fish containing the greater amount. 



The large-mouthed black bass, the yellow perch, the black crappie, the golden 

 shiner, and the mud minnow did not appear in Forbes's list. 



Food of trout, by Chancey Juday. 



Kind of trout. 



Locality. 



Number 

 examined. 



Length 

 in centi- 

 meters. 



Number 

 eating 

 Cole- 

 optera. 



Average 

 percent- 

 age of 

 Coleop- 

 terous 

 food.i 







19 



20-70 



4 



73 





do 



64 



10-20 



25 



42.7 





do 



106 



15-45 



37 

 1 



22.2 





do 



29 



2. 5-5 



5 





do 



126 



10-33 



43 



15.7 



Salmo whitei 



Kaweah River 



12 

 6 



14-20 



6 



30 





Soda Creek 



11-18 



2 



12.5 





Little Kern River 



41 



12-20 



38 



15 





Volcano Creek 



18 



12-28 



12 



2 









1 The total food is considered 100 per cent. 



It should be noted first of all that Doctor Juday (1907) made no distinction 

 between aquatic and terrestrial beetles, nor between adult and larval forms. In all 

 probability terrestrial species formed a large proportion of the total amount. This 

 is especially true of the trout captured in running water. To judge from the long 



