20 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
Length, 11 to 11.5 mm. 
Redescribed from one male and one female, Cauri Valley, Venezuela 
(Boston Society of Natural History, correctly identified by C. W. 
Johnson); one female, Kiaeteur, British Guiana (American Museum) ; 
and a pair from British Guiana (British Museum). 
MESEMBRINELLA RANDA Walker. 
Dexia randa WALKER, List Dipt. Ins., vol 4, 1849, p. 852. 
Ochromyia quadrilineata Fasricius of Surcouf, Revis. Musc. Test., p. 66, text 
fig. 5, and pl. 3, fig. 2. 
Male and female.—Greatly resembling quadrilineata, but less 
brightly colored. The front of the male is the same, and also the 
pollinose thoracic stripes; the abdomen, however, is slightly pruinose 
and bluish, not polished purple, and the third segment lacks the stout 
marginal row. This last is the main structural difference, as the 
chaetotaxy is otherwise the same. The middle and hind tibiae are as 
in quadrilineata, their femora, however, hardly so slender and elon- 
gated. 
Length, 10 to 11.5 mm. 
One male and one female, Brazil (British Museum), compared with 
the type of randa by Major Austen. 
Five additional females agree, but lack the subcostal blackish stripe 
in the wing, thus corresponding with the supposed type of guadrilineata 
which was redescribed by Surcouf. I can hardly make this out a 
distinct specific character here, though it seems usually constant. 
One of these females was from French Guiana, sent me by Professor 
Bezzi, identified as quadrilineata by Surcouf and mentioned in his 
Revision; two are from Kiaeteur and one from Tukeit, in British 
Guiana (American Museum); the other from Surinam (Johannsen). 
MESEMBRINELLA DORSIMACULA, new species. 
Male.—A rather slender yellow species, with the blue color on the 
abdomen very distinct but reduced to much smaller area than usual. 
Wholly yellow except the scutellum and a large spot immediately 
before it, which are deep brown and somewhat metallic; and a blue 
area including the fourth abdominal segment, most of the third above, 
and a small median posterior spot on the second: middle and hind 
tibiae brown. Front at narrowest at least twice the width of the 
ocellar triangle. Chaetotaxy: acrostichal 0,1; dorsocentral 2, 3; 
humeral 2; posthumeral 1; presutural 1; notopleural 2; supraalar 3; 
intraalar 2; postalar 2; sternopleural 1,1; scutellum with 1 apical, 1 
lateral, 1 discal. 
First abdominal segment with a well-developed vertical row of five 
bristles at the side (laterals); second with only one; third with scat- 
tered marginal row of six ending abruptly at the side; fourth with 
