138 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



the case of the predacious asihd flies. Dragonflies, Hemiptera. Man- 

 tidae, and Locustidae." (Poulton, E. B., Essays on evohition, p. 318, 

 1908.) 



Arachnida.- — ■" Spiders are for the most part not very particular as 

 to the insects they catch." (Bristowe, W. S., Proc. Zool. Soc. Lond.. 

 1929, p. 643.) 



" It is quite probable .... that certain species of spiders, together 

 with Mantides and other predacious insects, will be found to be among 

 the chief, perhaps the chief non-parasitic enemies of aposematic 

 insects." (Poulton, E. B., Trans. Ent. Soc. Lond. 1902, p. 327.) 



Pisces. — " In general, fish are opportunists as far as their food 

 is concerned. They eat what animal food is available, regardless of 

 the origin." ^ 



The closeness with which the brook trout is guided by availability 

 in its choice of food is indicated in the following table by Dr. P. R. 

 Needham based on studies near Ithaca, N. Y. : 



Comparison of .-IvaUable Aquatic Fish Foods in Stream Bottoms and Aquatic 

 Foods Consumed by Trout ^ 



Order 



Mayfly nymphs 



Caddisfly larvae and pupae 



Stonefly nymphs 



Fly larvae and pupae 



Beetle larvae 



Crayfish and shrimps 



Miscellaneous 



Totals 



2,316 



1,335 

 921 



869 

 476 

 235 



125 



6,277 



36.90 



21.27 



14.67 



13.84 



7.58 



374 



1.99 



356 

 528 

 41 

 187 

 33 

 14 

 23 



99.98 



1. 182 



30.12 

 44.67 

 3.47 

 15.82 

 2.79 

 1. 18 

 1.94 



99.99 



' Quantitative studies of the fish food supply in selected areas, Suppl. i8th Ann. Rep. 

 New York Conserv. Dep. 1928, p. 227, 1929. 



Further testimony to the effect of availability on the food of fishes 

 is contained in Muttkowski's study' of "The Fauna of Lake Men- 

 dota " in which he shows that insects form about 60 per cent by bulk 



* Muttkowski, R. A., The ecology of trout streams in Yellowstone National 

 Park, Roosevelt Wild Life Ann., vol. 2, no. 2, p. 229, Oct., 1929. 



"Muttkowski, R. A., Trans. Wisconsin Acad. Sci. Arts and Letters, vol. 19, 

 pp. 374-482, 1918. 



