426 PROCEEDINGS OF THE AMERICAN ACADEMY. 



C. amer- ^j^^^^f"" P. pili- P. den- P. vine' 

 icanus. ^"^{^ /era. lata, landica. 



Page Page Page Page Page 



Surrounding Queen 480 . . . 490 



Guarding 480 



Fighting 461 ... 481, 487 



Carrying 482 ... 



Kinds of Food 482 



Relation of Classes to various Ac- 

 tivities 462 ... 483 



In Barth Nests 465 483 



In Out-door Nests 467 485 



Correlation between Age and Func- 

 tion 471 



Conclusions for each Species ... 464 473 488 490 490 



VII. Discussion 491 



VIII. Summary 501 



IX. Bibliography 502 



X. Explanation of Plate 508 



I. Introduction. 



It is my purpose to state in the present paper the results of some 

 observations and experiments on division of labor among ants, espe- 

 cially in relation to size and structural differences of individual 

 workers and of classes. These studies have been carried on, with 

 interruptions, since September, 1904, chiefly at the Museum of Com- 

 parative Zoology, at Cambridge, Mass., under the guidance of Dr. 

 E. L. Mark, to whom I am deeply grateful for kind and valuable 

 assistance, but also in part at several other places, especially in sum- 

 mer, viz., at the Marine Biological Laboratory, Woods Hole, Mass., at 

 the Biological Laboratory of the Brooklyn Institute of Arts and Sci- 

 ences at Cold Spring Harbor, Long Island, at Ogunquit, Maine, and at 

 Randolph, N. H. I wish to express my obligations to Dr. W. M. 

 Wheeler for help in identifying species and for many suggestions. 



II. Historical. 



Many writers have for a long time maintained that among ants 

 there is a division of labor correlated with differences of size and 

 structure. While some of this work has been done either by experi- 

 ment or observation in the laboratory, or in the field, with this question 

 as the main point, much of it has been more or less incidental, the 

 student giving attention to this subject only as a side issue of other 

 work. 



There are some differences of opinion as to the functions of the 



