AEDES SPENCERn 725 



Male. — Proboscis moderately long, straight. Palpi about as long as the pro- 

 boscis ; apex of the long joint and the last two joints thickened, clothed with 

 long, dense, dark brown hairs; vestiture of blackish scales with violet luster, 

 some grey ones intermixed, patches of white scales towards apex of long joint 

 and at bases of last two joints. Antennte plumose, the last two joints long and 

 slender, rugose, pilose, black, the others short, black at insertions of the hair- 

 whorls ; hairs long, dense, dark brown. Coloration similar to the female, the 

 vestiture sparse throughout. Wings narrower, the stems of the fork-cells 

 longer, the vestiture sparse. Abdomen long, slender, depressed, without median 

 dorsal stripe, the dark scales predominating and with purplish luster; sides with 

 dense, long, pale ciliation. Claw formula, 2.1-2.1-1.1. 



Length : Body 5.5 mm. ; wing 4 mm. 



Genitalia (plate 27, fig. 185) : Side-pieces nearly three times as long as wide, 

 tips conically rounded ; apical lobe well removed from tip, rounded, prominent ; 

 basal lobe large, rounded, prominent, densely clothed with short setae with tuber- 

 cular bases, a large spine with accompanying hairs at base. Clasp-filament 

 slightly enlarged mesially, with a long articulated terminal spine and two small 

 setae from notches before the tip. Harpes broad, flat, with revolute edges, 

 tip thickened, pointed, point directed laterally ; haxpagones with a slender col- 

 umnar stem, thickened at base, a jointed apical filament broadening out mesially 

 on one side, the tip pointed. Unci invisible. Basal lobes small, rather approxi- 

 mated, each bearing four setse at tip. 



Larva, Stage IV (plate 123, fig. 426). — Head rounded, wider than long, 

 widest through eyes ; antennae rather short, spinose, the small tuft rather before 

 middle ; both pairs of dorsal head-hairs single, ante-antennal tufts of four hairs. 

 Tracheae broad. Skin smooth. Lateral abdominal hairs single on segments three 

 to six. Lateral comb of eighth segment of about nine large scales in an irregu- 

 larly doubled row. Air-tube stout, less than three times as long as wide, taper- 

 ing outwardly; pecten of about twelve long, sharp teeth, the last one or two 

 detached, reaching to near middle of tube, followed by a small hair-tuft. Anal 

 segment longer than wide, with a large dorsal plate, reaching well down toward 

 the ventral line ; dorsal hairs a long hair and a tuft on each side ; lateral hair 

 small, single; ventral brush well developed, with shorter tufts preceding the 

 barred area. Anal gills large, longer than the segment, tapering to a point, equal. 



The larvae develop in the early spring in the temporary pools of snow-water 

 upon the western prairies. There is but a single generation in the year and the 

 eggs overwinter on the ground. Mr. Knab made especial observations upon 

 this species. He says : 



" This is the common mosquito of the prairies of Saskatchewan, ajid appar- 

 ently occupies the entire northerly portion of the prairie region of North 

 America. It is very bloodthirsty, and its excessive abundance makes life upon 

 the prairie a torture during the early summer. The first larvae of this species 

 were found, newly hatched, at Oxbow, on May 6, in ditches along the railroad. 

 The weather continued cold for some time after this and the pools froze over at 

 night. This apparently did not injure the young larvae. On May 16 a large 

 number of pools were examined, and it was found that all but the larger pools 

 contained larvae. The pool from which the young larvae were obtained on May 

 6 now contained many larvae. It was deep and large and the water cool ; in con- 

 sequence the larvae were still in the second stage. In smaller, shallow pools, 

 where the water was warm, the larvae were much further advanced. A shallow 

 puddle in the field close by the railroad station, the water of which was remark- 

 ably warm, contained numerous larvae, mostly in the third stage. The larvae 

 for the most part kept among the grass close to the margin, where the water was 

 warmest and they were best protected from the wind. These larvae, brought 



