308 MICHIGAN SURVEY, 1908. 



DIPTERA OF THE 1905 UNIVERSITY MUSEUM EXPEDITION TO 



ISLE ROYAI^E. 



PROFESSOR JAMES S. HINE^ OHIO STATE UNIVERSITY. 



Much interest always attaches to a collection of insects from north- 

 ern regions and when Mr. Chas. C. Adams wrote and asked me to work 

 up the Diptera of the 1905 Isle Royale Expedition, I gladly accepted. 

 The collection is a small one and includes a number of common and 

 widely distributed species, but on the other hand it also includes several 

 species of special interest. Most of the specimens were collected by 

 Dr. H. A. Gleason, but he was aided by Mr. B. F. Savery. 



As the locality is not so far from midway between the East and the 

 West the question naturally arises as to whether the eastern or the 

 western species predominate in the niakeup of the fauna. This matter 

 is the more interesting to me for the reason that lately I have studied a 

 collection of Diptera from New England and also one from British 

 Columbia. After some study of species of Diptera from boreal regions 

 I am convinced that there is not the difference in the eastern and 

 western faunas in the North that there is in the South. There are a 

 number of species in the collection that are common to New England 

 and British Columbia, but there are others that so far are not proven 

 to have such a wide range, and it is with the latter that most interest 

 attaches in the consideration of our question. 



If the Tahanidae are considered we find that three species may be 

 said to be exclusively eastern and one exclusively western, while six 

 are distributed entirely across the continent. 



In the family Syrphidae are seven species that may be considered ex- 

 clusively eastern, and twelve species that reach clear across the conti- 

 nent, but not a single one that is exclusively western. 



In the Stratiomyidae the single species is eastern. So far as I can 

 find Isle Royale is the farthest west the species has been taken. 



In the Bomhyliidae one species is western, and the other reaches 

 across the continent. 



In the Therevidae the single species is western, Montreal being the 

 farthest east that specimens have been taken. 



In the Asilidae two species are eastern and one is western. The west- 

 ern species however is hardly typical. 



In the remaining families are several species that are exclusively 

 eastern and several that reach clear across the continent, but none that 

 are exclusively western. To sum up I find four western species and 

 more than a dozen eastern, while there are about thirty that occur from 

 the Atlantic to the Pacific. Therefore, although there are many species 

 common to Isle Royale and British Columbia, the following show that 

 the .general complection of the Isle Royale Dipterous fauna favors that 

 of eastern rather than that of western North America. 



