THE DIPTEROUS GENUS DOLICHOPUS IN NORTH AMERICA. 7 



able; but the undertaking had grown so large that I could not find 

 time to write the descriptions, nor could I make the drawings so neces- 

 sary to illustrate the many interesting sexual characters involved. 

 At length I hit upon the idea of a joint paper, Mr. Van Duzee to 

 prepare the text except the introduction, and Mr, Cole the figures. 

 Both of these colleagues, so admirably qualified for the respective 

 parts, responded enthusiastically, and I turned over my whole col- 

 lection, amounting to 139 species, to them. IMr. Van Duzee, more- 

 over, had collected in the family very energetically about Buffalo, 

 New York, and during a trip to the Pacific coast. By further active 

 collecting, by obtaining material from collectors and by visiting the 

 large museums, he succeeded in adding more than 50 per cent to the 

 collection that he received from me. Mr. Cole also obtained new 

 western material. 



Both the present work and my revision of 1893 are built upon the 

 foundation of Loew's monograph of 1864. A considerable list of 

 early descriptions which Loew discussed at length and was unablcto 

 identify, the types being either destroyed or in European museums, 

 are not herein mentioned at all; they will be found in Loew, and in 

 ni}' Catalogue of North American Diptera of 1905. Loew's types are 

 in the Museum of Comparative Zoology, Cambridge, Massachusetts; 

 they were examined by me in 1901, and in recent years by Mr. Van 

 Duzee. Both of us also studied the types in the American Museum 

 of Natural History, New York City. 



As far as possible the type of each new species has been placed in 

 the United States National Museum, while there are comparatively 

 few of the previously known species not found here; making in all 

 almost 200 species represented. Acknowledgment is due to many 

 collectors for their donations of type material, but especially to Mr. 

 Van Duzee himself. 



The technical history of the genus will be found in the following 

 bibliography: 



