V. 



Group Behavior 



IN THE second chapter I told of how I stumbled on 

 the fact that in the breeding season the normal be- 

 havior of isopods is affected by numbers present. 

 Such effects have long been known for many types 

 of behavior, and it would not be profitable here to 

 catalogue and analyze all the cases that are on record. 

 Rather, as before, I shall select certain well-authenti- 

 cated examples of breeding reactions and of other 

 types of behavior. Those which are chosen are espe- 

 cially noteworthy because of the behavior pattern 

 which is involved, or because freshly observed, or 

 both. 



And here is a shift in emphasis. I have been stress- 

 ing the existence of a widespread, fundamental auto- 

 matic co-operation which has survival value, and have 

 given evidence that it is a common trait in the animal 

 kingdom. In this chapter I shall discuss group be- 

 havior which may or may not have immediate sur- 

 vival value. In each instance, and throughout the 

 discussion as a whole, I shall be engaged in trying 



133 



