14 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
Male.—Head, thorax, abdomen, and legs brownish yellow, the 
abdomen except at base blue green, and a slight tinge of the same 
on the mesonotum in certain lights. Thorax with four whitish polli- 
nose stripes, more conspicuous in front; the intervening nonpollinose 
portions are, first, a median one between the acrostichals, and, sec- 
ond, one on each side beginning on the inner side of the humerus 
and the adjacent mesonotum, continuing mesad of the inner pre- 
sutural and halfway between the intraalar and dorsocentral rows; 
there is also a very narrow pollinose line along the anterior dorso- 
centrals. Front at narrowest three-fourths as wide as ocellar triangle; 
antennae, palpi, and proboscis yellow. Chaetotaxy: acrostichal 2, 3; 
dorsocentral 2, 3; humeral 3; posthumeral 3; presutural 2; noto- 
pleural 2; supraalar 3; intraalar 2; postalar 2; scutellar 1 apical, 
2 marginal, and 1 discal; sternopleural usually 2, 1, sometimes 1,1. 
A few pale slender hairs on attaching margin of hind calypter above, 
and usually some dark hairs on the middle of the vertical surface 
above it (behind postalar callus). Wing tinged with brown through- 
out, costa hardly darker, anterior cross vein infuscated. 
Female.—Front about one-fifth head width, the stripe above equal 
to four times one orbit; orbitals small and variable, the upper often 
minute or absent. The acrostichals just behind the suture some- 
times absent, and when this is the case the next posterior pair are 
sometimes absent also, or only one present. The paler specimens 
show the stripes most distinctly, and in these the wings have little 
infuscation except along the veins. 
Length, 7.6 to 10.5 mm. 
Two males from Bartica, British Guiana, determined by Surcouf 
as Ochromyia bicolor Fabricius; two males, two females, northern 
Yucatan (Gaumer), from the British Museum, determined as aene?- 
ventris Wiedemann by Van der Wulp in his Biologia paper; one 
male from Costa Rica, determined by Surcouf as Mesembrinella 
bicolor Giglio-Tos (all the preceding from Professor Bezzi, and 
mentioned by Surcouf in his paper). 
Fourteen males and nineteen females, Higuito, Costa Rica (Pablo 
Schild); one female, Piedra Negra, Costa Rica (Schild); two males, 
Tehuantepec, Mexico (Sumichrast) ; two females, Porto Bello, Panama 
(August Busck); one male, two females, Huachi, Bolivia (Wm. M. 
Mann); one male, two females, Bernardinos, Paraguay (K. Fiebrig); 
two females, Surinam and Venezuela (Professor Johannsen); one 
male, one female, Bartica, British Guiana (J. S. Hine). The last 
pair in my own collection; all the rest in the United States National 
Museum. 
Inasmuch as Mr. Surcouf divided his material generically on the 
number of sternopleurals, he naturally placed the material that he 
