AXOPHELES OCCIDENTALIS 1027 



Descriptiox of Female, Male, and Larva of Anopheles occidentalis: 



Female. Proboscis long, straight, slender; labellse long, lanceolate, dull 

 luteous, with small outstanding black setae; vestiture appressed, dark brown. 

 Palpi as long as the proboscis, uniform, slender ; vestiture of dark brown narrow 

 scales, roughened at base, a few stiff pale set at tip. Antennae filiform, the 

 Joints sul>equal. rugose, blackish, pilose; hairs of whorls sparse, black, short; 

 tori subspherieal, with a cup-shaped apical excavation, small, l)rown. Clypeus 

 elongate elliptical, brown, niide. Eyes well separated, black. Occiput with a 

 median groove, blackish, densely clothed with erect triangular, or notched, scales, 

 black at the sides, white in a large patch anteriorly, a tuft of white hair-scales 

 projecting forward between the eyes ; a row of black setae along margins of eyes. 



Prothoracic lobes lateral, small elliptical. Mesonotum narrow, elongate, 

 brown, strongly gray pruinose in a broad median stripe, a narrow median brown 

 line and the sides broadly dark broMai ; vestiture of short whitish hair-like scales, 

 densest anteriorly in three broad stripes ; some black bristles over roots of wings. 

 Scutellum collar like, luteous, with a marginal row of long blackish bristles. 

 Postnotum elliptical, prominent, dark brown, nude. Pleura? brownish and pale 

 intermixed, coxae luteous, with a few short hairs. 



Abdomen subcylindrical, somewhat depressed, truncate at tip, grayish brown, 

 rugose, apical margins of the segments shining black ; dorsal vestiture of numer- 

 ous short yellow hairs, longer dark ones at the sides. 



Wings "(plate 41, fig. 15) moderate, hyaline; petiole of second marginal cell 

 shorter than its cell, that of second posterior cell about as long as its cell ; basal 

 cross-vein distant about its own length from anterior cross-vein ; scales of veins 

 lanceolate, narrow, pointed, of different lengths on different areas, the long ones 

 black, the short ones brown, the black scales forming spots at bases of second 

 marginal and second posterior cells, at the cross-veins and on basal portion of 

 second vein ; an ill-defined metallic yellowish-coppery spot at tip of wing upon 

 the fringe, the rest of fringe dusky. " Halteres with pale stem and black knob. 



Legs long and slender ; vestiture brownish-black with a bluish reflection, tips 

 of femora and tibiae narrowly whitish. Claw formula, 0.0-0.0-0.0. 



Length : Body about 5 mm. ; wing 5 mm. 



Jllale. Palpi as long as the proboscis, last two joints swollen and club-shaped, 

 furnished with a tuft of hairs, yellowish towards base ; vestiture bronzy black. 

 Antennae plumose ; last two joints long and slender, rugose, pilose, black, the 

 others short, whitish, with black basal rings; hairs of whorls long, dense, 

 brownish. Coloration as in the female. Abdomen long, depressed, black ; lateral 

 ciliatiou of rather al)undant pale hairs. Wings narrower than in the female, 

 stems of the fork-cells longer, vestiture more sparse. Claw formula, 2-0.0-0.0. 



Length : Body about 5.5 mm. ; wing 4.5 mm. 



Genitalia (plate 41, fig. 270) : Side-pieces over twice as long as wide, tips 

 conically rounded ; a stout seta near middle of inner margin, two approximated 

 ones near base, another pair upon an inner lobe. Clasp-filament long, slightly 

 attenuated mesially, with a small articulated terminal claw. Unci columnar, 

 with a group of stout sette projecting outward at right angles. 



Larva, Stage IV. The larva is very similar to that of Anopheles quadri- 

 maculatus. It differs by the al)sence of the small rudimentary pair of floats 

 present on the second abdominal segment of that species. 



The larvfe live in ground-pools, preferably those of permanent water con- 

 taining alga^. Miss McCracken found them in a creek, a pasturage trough, tank 

 overflow, roadside pool, and the edges of a lake. Quayle found the larvae m 

 abundance in distinctly brackish water. Dr. Dyar found them m the grassy 

 edges of lakes and ponds, and, at Chico, California, Avhere they were abundant, 

 in all sorts of water ; in Nevada they occurred in pools in irrigated fields. 



Western United States, from southern California to Alaska, eastward through 

 Canada to northern Maine. 



