8 ANIMAL LIFE AND SOCIAL GROWTH 



system of mutual relations which bind the com- 

 munity into the loosely organized unit that it is. 



In the food of the black bass are to be found 

 fishes of different species at different ages of the 

 individual which represent all the important 

 orders of fishes; insects in considerable numbers, 

 especially the various water bugs and larvae of 

 may-flies, crayfishes, fresh water shrimps and a 

 smaller crustaceans of many species and of several 

 orders. 



On looking at the food of the fishes which the 

 black bass eats, it is found that one of these lives 

 on mud, algae and small Crustacea; another takes 

 nearly every animal substance in the water, in- 

 cluding mollusks and decomposing organic mat- 

 ter. The crayfishes are nearly omnivorous; 

 while of their relatives, some eat still smaller 

 crustaceans, some eat algae, and others live on 

 protozoans. At only the second step in what we 

 may call a food-web, we find the black bass re- 

 lated to every class of animals, to many plants 

 and to decaying animal and plant materials in 

 the mud of the lake bottom. 



Turning to the competitors of the black bass, 

 which are extremely numerous; all the young lake 

 fishes except the suckers feed at first almost 

 wholly on small crustaceans, so that the newly 

 hatched black bass finds himself launched into a 



