AMERICAN DIPTERA. 139 



Deromyia, Stenopogon, and Cophura, especially of the last two, 

 due, in the one case to variation, in the other to an assemblage 

 of what the writer believes to be a somewhat heterogeneous 

 collection of species. 



Terms used are fully explained in Smith's Glossary of Ento- 

 mology. The Schiner system of nomenclature for the wing 

 venation has been used. 



The writer wishes to express his gratitude to Doctors Charles 

 H. and Henry T. Fernald for the many ways in which they 

 aided and guided him in his work, to Prof. C. W. Johnson 

 for his continued interest and assistance for the start, to Dr. 

 S. W. Williston for valuable suggestions and that liberality 

 so encouraging to a new worker, to Mr. D. W. Coquillett for 

 assistance in very many ways, to Mr. Samuel Henshaw for 

 the privilege of several times studying the Loew and Osten 

 Sacken type collections in his charge at the Museum of Com- 

 parative Zoology of Harvard University, and to Dr. L. O. 

 Howard, Dr. H. Skinner, Mr. W. Beutenmuller, and Mr. C. 

 Schaeffer for the privilege of study at the National Museum, 

 American Entomological Society of Philadelphia, American 

 Museum, and the Brooklyn Institute, respectively. The 

 writer also wishes to express his obligations to those who have 

 made this paper more complete by the gift and loan of type 

 and other material. Although this material has been secured 

 through Dr. H. T. Fernald, who has kindly assumed all re- 

 sponsibility, as to the one most benefitted, I wish to thank 

 most heartily, besides all the above-mentioned gentlemen, Dr. 

 F. H. Snow, Dr. E. P. Felt, Prof. R. A. Cooley, Prof. J. M. 

 Aldrich, Prof. F. Sherman, Jr., Prof. C. P. Gillette, and many 

 others who have been of assistance in a similar way. 



SYSTEMATIC WORK. 

 Linnaeus in the tenth edition of his Systema Naturae placed 

 all the Asilidae in the genus Asilus. Scopoli, in 1763, erected 

 the genus Erax, and in 1803 Meigen, in Illigers Magazin, 

 divided the Asilidae into the genera Dasypogon, Leptogaster, 

 Laphria, and Asilus L. The Asilus of Meigen's classification 

 included Erax of Scopoli. This Meigen classification was ac- 



TRANS. AM. ENT. SOC, XXXV. APRIL, 1909. 



