44 c Canadian Arctic Expedition, 1913-18 



Length, 4-5 mm. 



Locality: Bernard harbour, Dolphin and Union strait, Northwest Terri- 

 tories, August 16, 1915, in bed of river; same locality, July 10, 1916 (F. Johan- 

 sen). 



With this last lot there a number of larvae of which I dissected the heads 

 of two. In most respects these larvae resemble the larva of johannseni Hart, 

 but the anal respiratory gills are withdrawn in all the examples so that it is 

 not possible to say what they are like structurally. 



I have drawn some of the cephalic parts as a better index to their structure 

 than a written description. One striking feature in the species is the very 

 conspicuously darkened third antennal joint. In most species the antennae 

 are uniformly coloured. Structurally the larva is a true Simulium and very 

 likely that of the last described pupa; both probably belong to borealis sp. n. 

 For details of mandibles, labium, antennae, and maxilla, see PL VII, figs. 7, 

 3, 2, and 1, respectively. 



In all specimens of the pupae of this species there are either fifteen or sixteen 

 thoracic respiratory branches, usually with two or three much shorter than the 

 others, and the arrangement differs noticeably from that in vittatum which 

 always has the branches paired to near base and very re,gular in arrangement 

 and length. 



LEPTID^. 



There is one specimen of a species of Ptiolina in the collection. I have 

 already described this species in a paper on the Diptera of Pribilof islands which ' 

 is now in press. 



Ptiolina arctica Malloch. 



One male, Bernard harbour. Dolphin and Union strait. Northwest Territories, 

 July 18, 19, 1915 (F. Johansen). 



EMPIDID^. 



This family is usually well represented in collections from northern latitudes 

 and in the material before me there are over twenty specimens representing 

 six species of the genus Rhamphomyia. 



The larvae of the species which I have found in Illinois- are predaceous, and 

 live in earth and decaying wood or leaves. Some species are ^quaitic in the 

 larval and pupal stages. The imagines of the genera Empis, Rhamphyomyia, 

 and Hilara are met with in swarms similar to those of Chironomidae and Culicidae, 

 performing a rhythmical aerial up and down flight generally in the lee of a bush 

 or tree, but some species, especially of Hilara, fly over water, notably close to 

 the surface of pools in streams. The imagines of most species are predaceous, 

 and in some cases the males capture the prey, fly past a swarm of females with 

 it, inducing females to pursue them, and in the- process of transference of the 

 prey to the female copulation takes place. 



Rhamphomyia Meigen. 



This, the only genus of the family in the present collection, is represented 

 by six species and twenty-two specimens. I have experienced so much trouble 

 in attempting to identify species of this genus through the lack of synopses 

 in the papers I have used that I have drawn up a key to those dealt with in 

 this paper in the hope that subsequent students may find it useful in identifying 

 collections from this region. With one exception I have failed to associate 

 the species before me with any previously described, and even in the case of the 



