4 CATALOGUE OF NORTH AMERICAN DIPTERA. 



Professor J. H. Comstock extended courtesies when I was visiting 

 Cornell. In his department I examined a considerable collection of 

 Diptera determined by Osten Sacken and \Yilliston, also some inter- 

 esting literature. In the Cornell University library I found " Silli- 

 man's Journal." 



Mr. Samuel Henshaw assisted me very kindly when I examined 



some families in the Loew-Osten Sacken collection at Harvard Uni- 

 versity. 



Dr. Garry de N. Hough gave me some unpublished notes, and a 

 large number of Diptera. 



Mr. O. A. Johannsen, of Cornell University, revised the classifica- 

 tion of the Chironomidae for me, greatly improving my work on that 

 family. 



Mr. Hugo Kahl gave me unpublished notes of his own ; he also 

 gave me minute directions about some points to look up in the Loew- 

 Osten Sacken collection, the outcome of which gave me a very high 

 opinion of Mr. Kahl's acuteness in systematic work, and revealed some 

 peculiar errors of Loew in describing two or three species. 



To W. D. Hunter, C. W. Johnson, C. T. Brues, and Professors 

 V. L. Kellogg and C. V. Piper, I am indebted for references to 

 literature. 



Mr. A. L. Melander gave me great assistance in the Empididse. I 

 have followed his advice quite uniformly in regard to nomenclature 

 and synonymy in that family. 



I have availed myself of Dr. Coloman Kertesz's great work, " Cata- 

 logus Dipterorum," of which two volumes have reached me, only to 

 the extent of adopting the generic distribution of the Cecidomyidae, 

 and of picking up one species Cnle.v penafieli Will. which I had not 

 found before. My work was almost completed when the first volume 

 of Kertesz came out. 



To all the gentlemen named, I extend my sincere thanks. 



The catalogue closes January I, 1904. 



J. M. ALDRICH. 



UNIVERSITY OF IDAHO, 

 January 27, 1904. 



