ART. 11. GENUS MESEMBRINELLA GIGLIO-TOS——ALDRICH., 13 
Wings strongly infuscated, first posterior cell a little paler in the 
middle and very widely open at margin, the intercepted costal seg- 
ment two-thirds as long as the posterior cross vein; second costal 
segment longer than the following; third vein remarkably straight 
from cross vein to tip. 
Length, 13 mm. 
One male, Tucurrique, Costa Rica (Schild and Burgdorf); one 
male, one female, lent by Professor Bezzi, labeled “‘Archidona, Kcua- 
dor, R. Haensch S.”’ This pair was placed by Mr. Surcouf along 
with two other females with the same label, under the name 
“ Mesembrinella quadrilineata G.'T. nec Fabricius.’”’ The pair, which 
I place provisionally under umbrosa, are larger than the others from 
the same place, and have the apical cell more widely open and the 
third vein bowed back toward the apex, besides having the stem of the 
venation bare. They differ from my Costa Rica type specimen, as 
far as I can make out in their poor condition, only in having a heavy 
subcostal infuscated stripe in the wing. 
Two females from the British Museum ; one of them from Cache, 
Costa Rica, was identified by Van der Wulp in Biologia as bicolor 
Giglio-Tos ; the other is from Balzapamba, Ecuador, and is aberrant 
in having fulvous bristles and hairs, except the largest bristles, on 
the pleurae, coxae, femora, and tibiae. I can not decide whether 
this is a specific difference or not. One additional female, Bolivia 
(Johannsen). 
Van der Wulp’s figure of what he called bicolor Giglio-Tos shows a 
venation about as in umbrosa except that the first posterior cell is 
too much narrowed at the tip; Wulp also noted the long second seg- 
ment of the costa in his text. 
Type.—Male, Cat. No. 25246, U.S.N.M. 
MESEMBRINELLA BICOLOR Fabricius. 
Musca bicolor Faxsrictus, Systema Antl., 1805, p. 291.—WIEDEMANN, Auss. Zweifl. 
Ins., vol. 2, 1830, p. 392. 
Calliphora socors WALKER, Trans. Ent. Soc. Lond., n. ser., vol. 5, 1860, p. 311. 
Mesembrinella bicolor, new species, Gieiio-Tos, Boll. R. Univ. Torino, vol. 8, No. 
147, 1893, p. 4; Ditteri del Messico, vol. 4, p. J1 (Mem. R. Accad. Sci. Torino, 
ser. 2, vol. 45, 1895). 
Mesembrinella aeneiventris VAN DER WuLP, Biologia Cent. Amer. Dipt., vol. 2, 
1896, p. 301, pl. 7, fig. 19. 
Ochromyia bicolor FasBricius and Mcsembrinella bicolor Giaui0-Tos, Surcouf, 
Revis. Musc. Test., pp. 70, 76, pl. 3, fig. 6. 
The type locality was ‘South America.”’ Giglio-Tos and Van der 
Wulp described it from Oaxaca, Playa Vicente, and northern Yuca- 
tan, considerably farther north than any other of the genus. The 
synonymy of socors I make out from specimens sent me by Major 
Austen, which he compared with Walker’s types. 
