PSOROPHORA VIRESCENS 543 



whorls long, dense; second joint with many erect black scales. Coloration 

 similar to the female. Abdomen elongate, depressed, with black lateral eilia- 

 tion, the dorsal vestiture metallic blue throughout. Wings narrower than in the 

 female, less strongly infuscated, the stems of the fork-cells longer. Claw 

 formula, 2.1-2.1-1.1. 



Length : Body about 5.5 mm. ; wing 4.7 mm. 



Genitalia (plate 20, fig. 141) : Side-pieces conical, about twice as long as 

 wide, without basal or apical lobes; clasp-filament large, inflated, distorted, 

 bifurcate, inner fork projecting inwards at a right angle, thick, rounded, its 

 terminal third again bent inward at a right angle, outer fork parallel to inner, 

 more slender, shorter, not bent at tip, with a small inserted terminal spine. 

 Basal portion of clasp densely setose. Harpes erect, columnar, concave, tips bent 

 over sharply and terminating in several small teeth. Harpagones large, slender 

 at base, expanding outwardly, the tip widened into a large round circular head 

 densely covered with very numerous short setae. Unci approximate, tips conical, 

 separated, lateral margins revolute wath an angular projection towards summit. 

 Basal lobes not developed. 



Larva, Stage IV (plate 114, fig. 387). Head subquadrate, wider than long, 

 posterior angles rouuded; eyes on an irregular prominence; antennae inserted 

 laterally on an angled prominence ; front margin shallowly emarginate. An- 

 tennae cylindrical, nearly uniform, sparsely spined all over, a single hair at outer 

 fourth, articulated terminal processes and a long spine, three times as long as 

 processes. Eyes large, divided, the larger anterior part pointed. Upper pair of 

 dorsal head-hairs single, lower double; ante-antennal hair double. Mouth- 

 brushes inserted on outer angles of head, folded downward and backward. 

 Mental plate triangular, with a large central tooth and eight on each side, pen- 

 ultimate one large and projecting. Mandible quadrangular, convex without, 

 smooth, a single appendage near tip; an outer row of few coarse filamentous 

 setae ; dentition of two long teeth, the first very long and curved, bearing three 

 small but wide teeth on its inner aspect, the second shorter, with five small teeth 

 on its inner edge ; a group of three little teeth below ; a small projection at angle ; 

 a row of fine setae near base. Maxilla rectangular, palpus projecting well be- 

 yond outer angle, a row of short spines on outer margin. Palpus twice as long 

 as broad, tapering a little to a truncate tip, the terminal digits rudimentary. 

 Thorax rounded, about as wide as long, anterior margin strongly convex ; lateral 

 single hairs long, tufts short. Abdomen stout, segments transverse, anterior 

 ones strongly projecting laterally; lateral hairs multiple on basal segments, 

 double on fifth, single on sixth ; secondary hairs in small tufts. Tracheal tubes 

 large, band-shaped, scarcely enlarged in thorax. Air-tube stout, conically ta- 

 pered from near base, tip less tapered, four times as long as wide; pecten reach- 

 ing to middle of tube, long; single tooth a quadrangular scale with excavated 

 base and roundedly furcate apex, one branch produced into a long hair ; a single 

 hair beyond middle of tube and beyond pecten. Lateral comb of eighth segment 

 a long curved row of scales preceded by an area of minute scales ; single scale 

 with three terminal spines, the middle one of which is lengthily produced; 

 small teeth mostly narrow and elongate, terminated in a row of cilia. Anal 

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

 brush on each side ; a double lateral hair ; ventral brush a series of short tufts 

 running the whole length of ventral line. Anal gills very long, twice as long 

 as the segment, regularly tapered to a sharp tip. 



Mr. Knab found these larvae in a small ditch of muddy water with larvae of 

 Psorophora discolor, in puddles of muddy water in a dry stream-bed with 

 Psorophora toltecuvi, in a large muddy puddle in the bed of a stream with 

 Culex larvae, in a ditch of nearly stagnant water in a town without other larvae 



