892 MOSQUITOES OF NORTH AMERICA 



blackish scales and with six very narrow rows of larger, narrowly lanceolate, 

 brilliant white scales, almost identical in arrangement with those of Orthopo- 

 domyia signifer; two of the rows are subdorsal and extend over the anterior three- 

 fourths of mesonotum; two are submarginal and extend the entire length of 

 the mesonotum; halfway between the subdorsal and submarginal stripes are 

 short stripes extending from middle of mesonotum to a point opposite anterior 

 angles of antescutellar space; halfway between the posterior ends of the two 

 pairs of discal stripes begins a pair of posteriorly converging lines of long sub- 

 erect white scales, continued over the scutellum where some very long white 

 scales extend out behind more than the entire length of the scutellum ; bristles 

 coarse and long, black. Scutellum large, median lobe prominent and broadly 

 rounded, with three groups of long black setae; beside the two lines of white 

 scales above described there are patches of white scales on the outer lobes. Post- 

 notum prominent, elliptical, with indication of a median ridge, nude, brown. 

 Pleurae and coxse dark brown and luteous, clothed with elliptical white scales 

 and with dark setae. 



Abdomen subcylindrical ; dorsal vestiture dull-black ; anterior angles of seg- 

 ments broadly white scaled ; first segment mostly dull-white scaled ; venter 

 dark scaled ; lateral cilia and those on hind margins of segments long and rather 

 coarse, but scattered, pale brown. 



Wings rather narrow, hyaline; scales of veins broadly clavate, mostly dusky 

 brown, with some white ones intermixed, these latter showing a tendency to 

 form groups and patches ; a white patch in the region of the cross-veins, extend- 

 ing over second, third, and fourth veins and upper branch of fifth ; at the base 

 the first vein is heavily white scaled for a short distance ; sixth vein white scaled 

 on its basal half; there are no narrow scales like those present in 0. signifer; 

 second marginal cell long, about twice as long as its petiole; posterior cross- 

 vein more than its own length behind anterior cross-vein. Halteres large, pale, 

 with white scales on the knobs. 



Legs long and rather slender; vestiture blackish-brown marked with white; 

 femora and tibiae with scattered white scales; knees narrowly and apices of 

 middle and hind tibiae silver-white scaled; anterior tarsi unicolorous, middle 

 and posterior ones white marked; middle tarsi with first segment rather nar- 

 rowly ringed with white at base and apex and with scattered white scales, second 

 segment with a few white scales dorsally at base and apex ; hind tarsi with first 

 and second segments broadly white ringed at bases and apices, third with 

 narrow rings at base and apex; fourth and fifth segments with small silver- 

 white dorsal patches of scales at bases and apices. Claw formula, 1.0-1.0-0.0. 



Length : Body about 3 mm. ; wing 3 mm. 



Genitalia (plate 35, fig. 237) : Side-pieces over twice as long as wide, 

 conically tapered, with a low rounded basal lobe bearing three long stout setae ; 

 clasp-filament moderate uniform, smooth, with an articulated terminal claw. 

 Harpes concave, inner margin revolute and thickened, tip dentate. Unci 

 forming a basal cylinder, tips inwardly dentate. 



Larva, Stage IV (plate 129, fig. 449). Head elliptical, longer than wide, 

 rounded, not widened through eyes ; antennae moderate, subcylindrical, smooth, 

 the tuft before the middle ; both pairs of dorsal head-hairs multiple and long, 

 ante-antennal tufts multiple but shorter, tufts set nearly in a transverse line. 

 Abdomen with a dorsal plate on seventh segment and a large one on eighth, 

 reaching well down towards venter. Lateral comb of eighth segment of long 

 scales in two rows, overlapping ; scales in distal row few and much longer than 

 in proximal row ; single scale with body fringed, tip drawn out as long as body 

 of spine. Air-tube about three times as long as wide, tapered on outer half, a 

 single tuft before middle arising from a slight notch. Anal segment a little 

 longer than wide, ringed by the plate ; dorsal tuft a long hair and tuft on each 

 side; lateral hairs single, small; ventral brush short but dense, confined to 

 barred area; anal gills very short, rounded, upper pair twice as long as lower. 



