Diptera 41 c 



flattened on dorsum, laterally sloping ventrad and mesad, armed along the basal 

 two-thirds of its lateral margins with slender, slightly flattened hairs, and with 

 four long, flat hairs on apical third, venter of apical segment with a large bifid 

 protuberance. 



Length, 13 mm. 



Locality: Lake at Bernard harbour. Northwest Territories, June 26, 1915 

 (F. Johansen). 



In the vial with the specimens is a large sack-shaped cocoon or pocket 

 of a very tough consistency which may belong to this species. It is open at 

 one end and shaped somewhat like the cocoon of Simulium except that it does 

 not taper so much at bottom. The surface is coated in part with small pieces 

 of rotten wood. 



SIMULIID^. 



There are several lots of larvse, pupte, and imagines of this family in the 

 collection. The imagines, with few exceptions, are in very poor condition. 



The larva and pupa of one species, obtained at Bernard harbour, very closely 

 resemble those of Simulium vittatum Zetterstedt, but as is shown in the text 

 following it is specificially distinct. 



The larvse of this family are found only in running water, some species 

 preferring very swift streams with rocky beds, and particularly those parts of 

 the streams where there are falls or declivitous rock-surfaces over which the 

 water moves at an accelerated speed. Other species are found in streams with 

 only a moderate current, and since in these streams the bed is generally more 

 or less muddy and gives an opportunity for a weedy or grassy growth, the 

 larvse and cocoons are usually found attached to this growth or to roots or 

 fallen branches of trees in the stream. 



The imagines are predaceous, usually feeding upon the blood of mammals, 

 and are a great pest in certain parts of North America and Europe. As a general 

 rule the flies do not bite man, but they cause great discomfort by flying precipi- 

 tately against the face, and by getting into the hair. Their bite is more painful 

 than that of a mosquito. 



There are imaginal representatives of two genera and three species in the 

 collection. 



Prosimulium Roubaud. 



The only- species of this genus in the collection is apparently undescribed. 



Prosimulium borealis, n. sp. 



Male. Black, opaque. Thorax and abdomen with yellowish white hair. 

 Wings clear. Halteres brown. 



Head as in hirtipes Fries, the antennse rather slender, postocular cilia dark. 

 Thorax with long, but not very dense, subdepressed hairs, those on posterior 

 margin and scutellum longer than those on disc; mesopleura with a few long 

 hairs near upper margin. Fore tarsus with basal joint slender, not so thick 

 but 1-5 as long as basal joint of mid tarsus; basal joint of hind tarsus almost 

 as thick as hind tibia, and nearly four times as long as second, not produced 

 at apex; second joint thickest a short distance before apex, three times as long 

 as its greatest diameter, and twice as long as third. Venation similar to that 

 of pecuarum Riley, the radial vein with third branch thickened at apex but not 

 distinctly furcate. 



Length, 3 mm. .... 



Type locality: Wollaston peninsula, Victoria island, summer, 1915 (D. 



Jenness). 



