Diptera 63 c 



— one on the posterior side at middle of fore pair, one to two on antero-ventral, 

 one to two on antero-dorsal, and one to two on postero-dorsal surface of mid 

 pair, one on antero-ventral, one on antero-dorsal, and one on posterior surface 

 of hind pair. Outer cross-vein in male at its own length from inner and at more 

 than that length from end of fifth vein, in female it is slightly more than its own 

 length from inner, and at its own length from end of fifth; last section of fourth 

 vein four times as long as penultimate in male, three times in female. 



Length. 6-7 mm. 



Type Locality: Bernard harbour, Dolphin and Union strait, Northwest 

 Territories, June, 1916, one male specimen (F. Johansen). Paratypes, same 

 locality, August 4, 1915 (F. Johansen); and Colville mountains, Wollaston 

 peninsula, Victoria island, July 22, 1915 (D. Jenness). 



In the collection I find one larva, and several puparia that agree with the 

 puparium mounted on the pin with the type specimen. These puparia (PI. 1 X 

 fig. 22) differ from any others in the family that I have seen. Descriptions of 

 larva and puparium follow. 



Larva. — Whitish testaceous. Cephalopharyngeal skeleton, locomotor 

 spines, and posterior spiracles black. 



General form similar to that of Anthomyiiine but the apical segment is 

 slightly more elongate, noticeably tapered towards apex, and the spiracles are 

 pedunculate, and situated upon two rounded fleshy elevations (PI. IX, fig. 25). 

 Antennae very minute; cephalopharyngeal skeleton well developed, mouth- 

 hooks paired, long and slender (PI. IX, fig. 24). Prothoracic spiracles not 

 developed; body very minutely striated, the segments well differentiated: 

 lateral fusiform area well defined; each segment except apical with four short 

 lateral longitudinal series of dark spot-like markings showing through the skin 

 (PI. IX, fig. 26); apical segment unmarked, anal opening at anterior margin, 

 with a pseudopod-like protuberance on each side which is about as long as its 

 basal diameter, tapered apically, and armed at apex with numerous short 

 thorns; the ventral surface of each of the other segments with three short 

 transverse series of dark spots, about three in number, the two outer situated 

 at middle, the central one slightly cephalad of these; locomotor spinules on all 

 except apical segment not noticeably elevated. 



Length, 10 mm. 



Puparium (PI. IX, fig. 22). Reddish brown, slightly shining, posterior 

 spiracular region black. 



Surface minutely transversely striated, and with much less distinct and less 

 regular wrinkles transversely on segments; anterior spiracles not distinguishable; 

 thoracic segments much less distinctly striated than abdominals, and with 

 microscopic locomotor setulse; each abdominal segment with an oval clump of 

 short black thorns on each side of median line on ventral surface, on each side of 

 the incisions also with a band of more minute spinules; antepenultimate segmenl 

 much constricted and more closely and distinctly longitudinally striated than the 

 others; anal opening in the form of an elongate slit surrounded by a slight rim 

 which encloses a broadly rounded dark brown area 1 -5 times as wide as long: on 

 each side of the anal opening and at a considerable distance from it there is a 

 small clump of short, black spines on a slight eminence; posterior spiracles 

 elevated, surrounded by a coarsely granulose blackened area, the openings small. 

 as shown in PI. IX, fig. 23. 

 Length, 12-5 mm. 



The larvae live in ponds and are truly aquatic. The principal characteristics 

 of the larvae arc the clumps of locomotor spines on abdomen, the pseudopod-like 

 anal locomotor organs, and the absence of prothoracic spiracles. The caudal 

 part beyong the constriction in puparium is not occupied by any part of the 

 enclosed imago after the induration of the larval skin, and forms an air chamber 

 which serves to keep the puparium at the surface, the posterior spiracles being in 

 this position and so held that they have direct contact with tin 1 atmosphere. 



