GROUP BEHAVIOR 1 39 



fusion effect arises which decreases the feeding effi- 

 ciency of the fish. 



It has been suspected for years that such a confu- 

 sion effect exists and has survival value for small 

 animals flocking together in the presence of a preda- 

 tor, such as small birds in the region of a hawk. 

 These observations of Welty's make the best demon- 

 stration that I know of the existence of such an 

 effect, in this case the Daphnia in the presence of the 

 fish. I am less interested in this confusion effect at 

 present than in the demonstration of social facilita- 

 tion in feeding, a phenomenon which has been 

 shown to exist for a number of fishes, including zebra 

 fish, paradise fish, goldfish and guppies of the more 

 usual aquarium varieties, and the lake shiner, No- 

 tropis atherinoideSy as well. 



None of these fishes is very social, that is, none 

 of them group into close schools. For evidence of 

 similar social stimulation among social animals it is 

 interesting to examine the effect of numbers present 

 on the digging behavior of the highly social ants. 

 The account of this work was published in 1937 by 

 Professor Chen of Peiping, China. (29) 



These ants, a species of Campanotus, dig their 

 nests in the ground. It was found that all the worker 

 ants of this species are capable of digging a nest 

 when in isolation, but that the rate of work varies 



