84 KELLOGG. [VOL. I. 



tracheae. The face is whitish, with a median longitudinal dark 

 line, and the antennary fossae with dark margins ; the basal 

 segment of the antenna is rather dark, the other segments pale. 

 Thorax without bristles, dark above, pale beneath. Legs long 

 and slender, whitish with blackish joints; middle and hind legs 

 longest and equal, front legs only a little shorter ; average meas- 

 urement of middle leg, femur i mm., tibia i mm., tarsus i mm.; 

 tarsus 5-segmented, segment i as long as segments 2, 3, and 4 

 together ; segment 5 slightly longer than segment 4 ; tibiae of 

 all legs with single apical spur ; tarsal claws strongly curved, 

 thickened at base, and with a few (three ?) delicate spines on 

 basal half; no pulvilli ; empodium (Fig. 2, enip.} rather long, 

 curving, filiform, and plumose or pectinate for its whole length. 

 Wings narrow, strap-like, extending only to fourth abdominal 

 segment, length .75 mm., and wholly without veins; whitish, 

 somewhat wrinkled, and finely spinulose. These strange vein- 

 less wings are not specially thin or delicate, but, on the contrary, 

 are rather thickened, the costal margin being especially thick- 

 ened and perhaps folded. The halteres (Fig. 3, //.), or the 

 structures which occupy the usual position of halteres, are not 

 of the usual pedicel and knob type common among Diptera, 

 but are minute, lobe-, or scale-like processes, appearing like 

 rudiments of metathoracic wings ; like the mesothoracic wings, 

 they are rather thickened and are finely spinulose ; they are 

 widest at base and taper to a rounded tip ; they average .08 

 mm. in length. Abdomen of nine segments, tapering gradually 

 posteriorly ; mottled gray and blackish above, lighter below, 

 palest laterally ; a few scattered, small, wholly inconspicuous 

 hairs, the body appearing glabrous ; external genitalia consist- 

 ing of a pair of large, conspicuous, strong, articulated claspers 

 (Fig. 3, cl.\ which are covered with a pubescence. 



Female (Fig. i).-- Length 2.5 mm., thus being one-fourth 

 longer than the male ; this extra length is all in the abdomen, 

 which is markedly larger in every way than the abdomen of the 

 male. The head and thorax are narrower than the robust 

 abdomen, which is sub-cylindrical, tapering only slightly poste- 

 riorly. Eyes as in male very small, very widely separated, and 

 hairy. Antennae (Fig. 3, ant.} only 4-segmented. Mouth-parts 



