1896.] Entomology. 1053 
Mammaria.—Dr. C. H. Merriam has recently revised the Lemmings 
of the genus Synaptomys, giving descriptions of three new species. 
He finds that this genus instead of being monotypic, comprises two well 
marked subgeneric groups—Synaptomys’ proper and Mictomys; that 
the first of these groups inhabits eastern Canada and northeastern 
United States from Minnesota to New Brunswick, and contains four 
fairly well defined forms; that Mictomys has a transcontinental dis- 
tribution from Labrador to Alaska, and contains at least four species. 
(Proceeds. Biol. Sc., Washington, Vol. X, 1896.) 
ENTOMOLOGY: © 
A New Era in the Study of Diptera.—The work done on 
the classification of North American Diptera falls naturally into three 
periods. The first ended with the publication of the “Catalogue of 
North American Diptera,” by Osten Sacken, in 1859. The descriptive 
work of most value previous to this time was by Wiedmann and Say, 
and a little by Loew toward the last. Harris, Macquart and Walker 
had also published numerous species; but there had been little coöp- 
eration, and it was nearly impossible to determine from the descriptions 
the synonyms that had been created. Osten Sacken recognized this 
condition, and did not attempt to solve such problems in his catalogue. 
The following nineteen years to the second edition of the catalogue 
in 1878 comprise the second period, characterized by the singular fact 
that the vast amount of work accomplished was almost wholly by 
Europeans. Walsh published some twenty species, Riley eight, and 
several others from one to four each—scarce forty in all—while Loew 
had in the same time performed the monumental work of describ- 
ing at least 1300 North American species, Osten Sacken had added 
several hundred, and Schiner and Thomson a considerable number. 
Moreover, the new edition of the catalogue was enriched with a vast 
fund of information gathered by the author in the study of American 
types in all the principal European collections, revising the synonymy 
and correcting the generic references as would have been impossible in 
any other way. About the time of the issuance of the catalogue, the 
collections of Loew and Osten Sacken were deposited in the Museum 
of Comparative Zoology, at Cambridge, Mass. This marked the con- 
clusion of what may well be called the Loew—Osten Sacken period. 
Loew died, and Osten Sacken retiring from the diplomatic service, re- 
sumed his residence in Germany. His dipterological writings since 
1 Edited by Clarence M. Weed, New Hampshire College, Durham, N. H. 
