THE ANIMAL COMMUNITY 7 



abundant food supply for the birds and other 

 insect-eating animals so that fewer than usual 

 will starve. Even though no other checking 

 force were to act, the increase of insect feeding 

 forms would in time bring the insect pests under 

 approximate control. This would no sooner be 

 established than another shift in weather, per- 

 haps a cold winter, would upset the whole balance 

 again. 



The effects produced by insects upon the basic 

 food plants show that plants as well as animals 

 are to be considered in such communities. This 

 means that life processes in a given community 

 are so interrelated that any development which 

 affects one important set of plants or animals in 

 the community, sooner or later, affects all. 



One of the best descriptions of the working of 

 this web-of-life in a non-human community is that 

 given by the late S. A. Forbes of the Illinois 

 Natural History Survey in his description of the 

 inter-dependencies of life in a small lake. It is 

 relatively easy, though sufficiently exciting to 

 be called sport, given the right body of water and 

 the proper season and bait, to lift a large-mouthed 

 black bass out of the water; but if one should 

 undertake to unravel all the tangle of interrela- 

 tions from which the fish had been so unceremo- 

 niously removed, he would see the complicated 



