VI BULLETIN 31, UNITED STATES NATIONAL MUSEUM. 



Prof. J. A. Lintuer, of Albany, Mr. G. F. Gaumer, of New Mexico, 

 and various others whose names will be found in their appropriate 

 places. To all these I would express my sincerest thanks. Nor should 

 I neglect to mention the extensive collections from the West and South- 

 west obtained from Messrs. H. K. Morrison and O. T. Baron, and from 

 San Domingo, from Mr. G. F. Frazar. 



Other kind favors, which 1 would gratefully acknowledge, were re- 

 ceived from Prof. H. A. Hagen, of Cambridge, who kindly permitted 

 me to study for several days in his laboratory the type collections of 

 Loew and Osten Sacken. IMy readers will pardon me in the pride I take 

 in stating that of nearly two hundred species which I had identified 

 absolutely independently from descriptions, I found upon comparisons 

 with the types and identified species in the Loew and Osten Sacken col- 

 lection but three or four discrepancies. I can give no higher praise to 

 the work of these two authors that admits of such close results. To 

 Mr. S. H. Scudder, my thanks are due for his kindness and courtesy in 

 permitting me to study his collections of fossil diptera and drawings. 

 To Prof. A. Van Name, the librarian of Yale College, my sincere thanks 

 are also due for his unfailing courtesy and assistance. Nor should I 

 neglect to speak of the encouragement and assistance that have been 

 aftbrded me by my wife. 



Of the published writings on this family, 1 have been mostly indebted 

 to tiiose of Schiuer, to whom the classification of the family owes much, 

 and to the writings of Loew, Osten Sacken, Wiedemann, and others, 

 wherever they were accessible. Of Baron Osten Sacken's work here, 

 as elsewhere, 1 cannot speak in terms of too great praise. His descrip- 

 tions are clear, accurate, and conscientious; I have never been in doubt 

 regarding the correct identification of his species in this family. How 

 mucli the present results are owing to his labors will be apparent to any 

 one who will even cursorily examine the following pages. My heartiest 

 thanks are likewise due him for the constant interest he has taken in my 

 studies, during the years that I have had the pleasure of correspond- 

 ence with him. Of Loew's work I need not speak. No better monu- 

 ment to a talented, learned, and versatile man exists anywhere in the 

 domain of dipterological literature — and this field has been cultivated 

 by most able, as well as poor workers — than in his Diptera Centuriae 

 and Monographs. Hi s Latin descriptions are models, and very much 

 of the synonymy of the Ameri(;an Syrphidas is due to him. Nor should 

 I fail to mention the conscientious work of Mr. P. M. v. d. Wulp, of 

 Holland. He has not written a great deal on North American diptera, 

 and that, unfortunately, is mostly in the Dutch language ; but what 

 he has written makes one wish that he had published more on our fauna 

 in the English language, which he uses with fluency. Mr. J. F. M. 

 Bigot, of Paris, has, with commendable zeal and industry, written much 

 on the North American Syrphidae ; his works may be consulted with 

 profit. 



