1923] 
North American Dixidce 
53 
bb. Tips of hind tibiae not so sharply differentiated. 
c. Petiole of R2+3 (measured on a straight line from its 
base to base of fork), less th'an ^ as long as R3; pro- 
boscis, scutellum, and knob of the halteres yellow; 
crossvein of wing very feebly clouded; r-m crossvein 
slightly distad of the base of R4+5. N. Y., terna Lw. 
cc. With other characters. 
d. Wing with one or more spots, 
e. The space between the bases of the cubitus and 
anal vein, between the branches of the cubitus, and 
the basal part of the anal lobe inf uscated; terminal 
clasper segment triangular, mesal process of basal 
segment forked (fig. 1), calif ornica n. sp. 
ee. With but a single, rather distinct spot on the wing, 
f. Petiole of R 2-|-3 and R3 subequal in length, wing 
spot very distinct, veins strongly marked; pro- 
boscis and scutellum blackish; halteres sordidly 
yellow; terminal clasper segment not tapering, 
truncate apically, mesal process of basal segment 
forked (fig 6). Me., N. Y. centralis Lw. 
ff. Petiole shorter; proboscis, scutellum, and halteres 
yellow, N. J.; Md. . . . notata Lw. 
dd. Wing spot very indistinct or wanting, 
e. The r-m crossvein is situated slightly proximad of the 
base of R4-1-5 thus intersecting the petiole of the 
radial sector; Sc endsopposite the base of Rs. St. 
Vincent Is. calvula Will, 
ee. The r-m cross vein is situated at or slightly distad 
of the base of R4+5 thus connecting this vein with 
the media. 
f . Dorsum of the thorax yellowish with thoracic darker 
stripes which may be more or less confluent; palpi 
dark. 
g. Proboscis yellow; scutellum and halteres black- 
ish; wing veins strongly marked, subcosta ends 
opposite to base of Rs; thoracic stripes black 
and more or less confluent, large part of the 
pleura yellow. Texas . venosa Lw. 
