682 HENRY FAIRFIELD OSBORN 
WORK ON THE DIPTERA 
We may for a moment divert our attention to Williston’s great 
work on the Diptera. At the Pittsburgh meeting of the Entomo- 
logical Society of America in 1917 he gave many interesting rem- 
iniscences of his early work; he showed that he turned to the 
Diptera when he despaired of securing original material in verte- 
brate paleontology. It is seldom that science has seen talent so 
evenly divided between subjects so remote as dinosaurs and flies. 
J. M. Aldrich, in his Catalogue of North American Diptera 
(Smithsonian Miscellaneous Collections, 1905), cites sixty-seven 
titles by Williston, covering the period from 1879 tg 1899, and adds 
this note: | 
An admirable feature of Williston’s work, which does not show fairly in 
the above list, is the attention he has given to identifying and redescribing the 
species of other writers. In all his longer papers this is a prominent part, 
frequently occupying as much space as the new descriptions, and requiring 
more time than they in preparation. 
This feature of Williston’s work was, in fact, the result of his 
ever-active desire to be helpful—the same desire which prompted 
him to prepare his Manual of North American Diptera, a book which 
is indispensable to a beginner in dipterology and a very great con- 
venience to advanced workers. It was this kindly, sympathetic 
spirit too which endeared him to his students and fellow- 
entomologists, while his accurate observations and keen judgment 
commanded respect everywhere. 
Williston practically ceased active work on flies twenty years 
before his death, although his interest in them continued, as was 
shown by occasional papers, especially from 1906 to roo8 and 
again in the later years of his life. He jokingly said in conversa- 
tion that he did not dare to think of flies lest he be tempted to take 
too much time from fossils. His collection of Diptera from the 
United States and Canada is now in the University of Kansas; the 
remainder of his collection, including much of the valuable material 
which he had collected while writing the volumes on Diptera in 
the Biologia Centrali-Americana, is in the American Museum of 
Natural History. 
