2 THE NORTH AMERICAN SPECIES OF DROSOPHILA. 



attempts to get them have been made. It nevertheless seemed desir- 

 able to discover whether the kind of differences that distinguish wild 

 species are also the kind that are appearing in the laboratory as muta- 

 tions. This question will be discussed in detail later in this paper. 



An attempt has been made to bring together here the more important 

 available information concerning the North American members of 

 the tribe Drosophilinse, and more especially the genus Drosophila. 

 Exotic forms are discussed occasionally, but no extensive treatment 

 of them has been possible. The data concerning the taxonomy, 

 anatomy, development, distribution, and habits of the group are pre- 

 sented as fully as available material will permit. Only a brief survey 

 of the experimental work on the group has been attempted, but a 

 bibliography of the experimental literature (with the more important 

 papers on other lines) is presented. 



ACKNOWLEDGMENTS. 



This study has been made possible only by the favors and encourage- 

 ment received from many difTerent sources. It would not be possible 

 to mention here all those who have helped in one way or another 

 toward the completion of the undertaking. There are, however, 

 several to whom my thanks are especially due. 



I have made extensive use of the collections and library of the 

 American Museum of Natural History, and am under great obliga- 

 tions to Dr. F. E. Lutz and Mr. A. J. Mutchler for the pains they have 

 taken to facilitate this use. Professor J. M. Aldrich and the late 

 Mr. Frederick Knab, at the United States National Museum, and 

 Mr. C. W. Johnson, at the Museum of the Boston Natural History 

 Society, have given me every facility for studying the material under 

 their care. Extensive loans of material from these three museums have 

 been of very great help. Through the kindness of Mr. Samuel Hen- 

 shaw and of Mr. Nathan Banks I have been enabled to examine the 

 Loew collection in the Museum of Comparative Zoology at Harvard. 



Loans of valuable material have been received from Mr. C. W. 

 Johnson, Professor J. M. Aldrich, Professor A. L. Melander, and Mr. 

 S. W. Frost. Dr. J. C. H. de Meijere has sent me several European 

 species, properly named, and these have been very valuable for com- 

 parison with American forms. Mr. C. G. Lamb has supplied valuable 

 information concerning several exotic forms about which I was in 

 doubt. 



Local collections of considerable interest have been sent to me by 

 several people. The most significant of these are the follow^ing: 

 Dr. 0. L. Mohr, from Norway; Professor J. Arias, from Spain; Mr. W. 

 S. Adkins, from Tennessee and elsewhere; Dr. R. R. Hyde, from 

 Indiana and Maryland; Dr. F. Pajoie, from Indiana; Mr. D. E. 

 Lancefield, from Oregon; Mr. C. T. Ramsden, from Cuba; Mr. L. L. 



