specimens. The dearth of such collections, both of ants and of all 

 other groups of insects, excepting, perhaps, the Coleoptera and Lepi- 

 doptera. has not ceased to be a great drawback to the study of ento- 

 mology in America. 



The bibliography (Appendix E), which has been carried down to 

 the close of the year 1908, is unfortunately very voluminous and includes 

 many titles of unimportant works. Like all such compilations, it is 

 necessarily incomplete, and undoubtedly contains positive errors. A 

 serious attempt has been made, however, to reduce these to a minimum, 

 and I shall be glad to receive any additions or corrections. 



For portions of the text and many of the figures I have drawn 

 rather freely on my previously published papers. A few entire chap- 

 ters, in fact, such as those on polymorphism, have been reproduced 

 with only slight verbal alterations. Others, like Chapters XYIII and 

 XX, are abridgments of longer accounts of the fungus-growing and 

 honey ants recently published in the Bulletin of the American Museum 

 of Natural History. 



I am under lasting obligations to Professor H. C. Bumpus for the 

 interest he has shown in the progress of my work, and the aid which 

 I received in its prosecution while I was Curator of Invertebrate 

 Zoology in the American Museum of Natural History. To Mr. Roy 

 W. Miner, Assistant Curator of Invertebrate Zoology in that institu- 

 tion, I am deeply indebted for much assistance in making out the table 

 of contents, and especially in arranging and verifying the bibliography. 

 Many of the illustrations have been made by Miss Ruth B. Howe. 

 My friend, Professor Oliver S. Strong, of Columbia University, has 

 most generously permitted me to use a number of the remarkable 

 photographs which he and Mr. J. G. Hubbard took of living colonies 

 of various ants in the possession of Miss Adele M. Fielde. Three of 

 my former pupils, Messrs. A. L. Melander, C. T. Brues and C. G. 

 Hartman. have also contributed several interesting figures, and Mr. 

 Brues has aided me in reading the proof. 



BUSSEY INSTITUTION, 



FOREST HILLS, BOSTON, MASS., 

 October 30, 1909. 



