564 



GEOLOGICAL SURVEY OF THE TERRITOEIES. 



Sericomyia militaris, Walk. (Colorado Mountains); the same insect 

 occurs frequently in Canada and also in the White Mountains. 



HelopMlus bilineatus, Curtis (Twin Lakes), first described from speci- 

 mens brought back by Captain Eoss from his polar cruise. I possess 

 it also from Labrador. 



ffelopJiilus, n. sp.! (South Park, Colorado), which I also received from 

 Fort Eesolution, on Mackenzie Eiver, and from other parts of the British 

 possessions. 



Chrysotoxum derivatum^ Walk., (Colorado Mountains), described by 

 Mr. Walker, from the British possessions in North America. I have 

 specimens from Alaska. 



Uristalis, two or three species (specimens principally from Twin Lake 

 Creek), which 1 could not identify with any species I know. 



3Ielithre]}tus, sp. (Twin Lake Creek), very like M. cylindricus, Say, 

 but apparently different. 



Syrplms eoroUce (Fair Play), vitripennis {!) and one or two others which 

 I could not identify. 



Syrphus obUquus, Say, was found above the tree-line. 



Family CEstrid^. 



The common horse bot, Gastrtis equi (Colorado Mountains). 



The families Tachinidce, Anthomyidw, Muscidce are represented by a 

 considerable number of specimens, although not so many species. I 

 will notice especially the frequent occurrence of species of Gonia in the 

 mountain-region, and a large Echinomyia from the plains. TIae common 

 blue bottle-fly has been found ascending the mountains above the tree 

 line. 



As the above-named families have not been worked up in the Eastern 

 States yet, it would be premature to attempt any further identification 

 of the species. 



The most interesting novelty in the whole collection is a species of the 

 family BlepJiaroceridce, a family rather anomalous in its structure, of 

 very doubtful position in the system, and counting, as yet, but a few 

 members. Only seven species, distributed among five genera, are known 

 from tbe whole world.* Four of these species are from Europe ; the 

 remaining three are from Ceylon, from South America, and from the 

 United States. The new species from Colorado is thus the eighth in the 

 group, and requires the formation of a new genus, the sixth in the 

 family. 



Bihiocephala, nov. gen. Closely allied to BlepJiarocera, but differing 

 prncipally in the venation of the wings, the shortness of the antennae, 

 and the structure of the head. I possess only male specimens. 



Eyes divided in two halves ; the upper one with larger and the lower 

 one with smaller facets; these 

 two halves are of nearly equal 

 size, (the upper one even seems to 

 be a little larger), and both are 

 clothed with a dense and short 

 microscopic pubescence; besides 

 this pubescence, the lower half 

 is beset with long^ erect ijile ; the 

 two halves are contiguous, and not separated by a narrow band, without 

 facets (at least, I am not able to perceive any such band). The eyes are 



"^All that is known about this family may be found in the paper " La famiglia del 

 Ble2)hnrocericli," hy H. Lloqw,. in the " BuUetino della Soc. entom. itaiiana," vol. i,p. 

 85-101, tab. ii. 



