the Dipterous Subfamily Ditomyine. 433 
The known genera of the Ditomyinz may be separated by 
the following key :— 
1. Radio-median cross-vein present; eyes 
entire, or only moderately emarginate, 
at any rate not nearly meeting ; 
antenne flattened (Ditomyini) : 
Radio-median cross-vein obliterated ; 
eyes deeply emarginate above the 
antenns, with narrow dorsal strips 
which almost meet in the middle line 
(in both sexes); antenne slender, 
cylindrical (Nervijunctini) ........ 4, 
2. Medio-cubital cross-vein vertical or 
even pti outwardly oblique, 
joining Cu, near the base; F2+3 
nearly parallel with R445, the base 
being strongly angulated or arched ; 
Mi+2 strongly curved at base, M, 
PAS BULBINE, Sve eee Leases . Centrocnemis. 
Medio-cubital cross-vein inwardly 
oblique, in a line with the longer 
basal portion of Cu,; R243 more 
divergent from £4+5, less arched at 
the base; M evenly forked ........ 3. 
3. Eyes moderately emarginate ; R2+3 not 
or scarcely longer than the second 
bo 
TORGOD OFFI e.g kan tiem ena .. Symmerus. 
Eyes entire; R2+3 much longer than 
the second POLHON OL RE vive. ne Ditomyita. 
4, Fusion of Mand &s very short; m-—cu 
outwardly oblique; 243 shorter 
than the second section of Rs...... Nervijuncta. 
Fusion of M and &s longer (when M 
is complete); m-cu vertical ; R243 
longer than the second section of Rs, 5. 
. Tip of wing truncate (in male only P); 
veins all well-marked ; ; Wings bearing 
scales in certain areas ............ Arctoneura. 
Tip of wing not truncate; parts of 
media and cubitus faint or absent ; 
wings without scales.............. [? Arctonewra, subgen. |Casa. 
or 
Centrocnemis was sunk under Symmerus by Johannsen, 
but appears to me to be well-distinguished ; it will include 
all the known Neotropical members of the subfamily, the 
Holarctic species all remaining in Symmerus. 
Centrocnemis fuscinervis, sp. n. 
Head dark grey; palpi blackish; antennz dark brown, 
the scape ochreous. Thorax grey, with an ochreous tinge ; 
mesonotum with three separate black stripes, scutellum 
ochreous; pubescence yellowish, bristles dark brown. 
