RIVELLIA. 383 
genus ; occiput black. Basal joints of the antenne rufous (the third joint is wanting). Thorax and 
scutellum black; thoracic dorsum with a short, dense, yellowish pilosity; pleure with some bluish 
metallic reflections; scutcllum with two bristles. Abdomen curved downward, rather broad at the base, 
attenuated towards the tip, somewhat metallic greenish-black, densely covered by a greyish pilosity ; 
genitalia on the ventral side with two appendages. Fore coxw yellowish-rufous, middle and hind cox 
black ; legs yellowish-rufous, the tibis and the terminal two or three tarsal joints brown. Halteres 
blackish. Wings greyish-hyaline; the brown pattern generally agreeing with that of the preceding 
species (2. micans), but the first cross-band is angular in shape, distinctly separated from the blackish 
base and, though less intense, prolonged to beyond the fifth vein. 
Hab. Mexico, Omilteme in Guerrero 8000 feet (H. H. Smith). 
A single male specimen. 
4, Rivellia conjuncta. (Tab. X. fig. 11, wing.) 
Rivellia conjuncta, Léw, Monogr. Dipt. N. Amer. iii. p. 88, t. 8. fig. 3 - 
This species is easily recognizable by the large extension of the blackish pattern on the wings, the cross-bands 
being much broader than in the other members of the genus. The first cross-band is fully connected 
with the black base and separated from the second only by a triangular hyaline spot at the costa; the 
first, second, and third cross-bands are largely coalescent at the hind margin of the wing, the third, 
moreover, is united at the costa with the fourth, which forms a rather broad border at the tip. 
Hab. Nortu America, Maryland 1—Mexico, Cuernavaca in Morelos, Amula and 
Chilpancingo in Guerrero (//. H. Smith); Costa Rica, Caché (Rogers). 
Several specimens of both sexes. 
5. Rivellia connecta, sp.n., ¢. (Tab. X. fig. 12, wing.) 
Shining black ; front and antenne brownish; legs black, the base of the tarsi yellowish ; the second cross- 
band in the middle largely united with the first, which is connected with the blackish base. 
Length 2°5 millim. 
Front brownish, as broad as the cyes, with parallel sides; face cinereous, perpendicular, not excavated ; 
clypeus large; occiput black. Antenne rufous; the third joint on the fore side and towards the tip 
infuscated ; arista pale rufous. Thorax, scutcllum, and abdomen shining black ; the abdomen ovate. 
Legs black ; the tarsi yellowish, but infuscated towards the tip. Halteres blackish. Wings hyaline; the 
first cross-band is broad and at the costa largely connected with the blackish base—inferiorly it reaches, 
though less intense, to beyond the fifth vein, and in the middle it is largely united with the second cross- 
band, which is much narrower, rather perpendicular, slightly concave at its outer side, and terminates at 
the fifth vein; between the first and second cross-bands there remain only two triangular hyaline spots— 
one at the costa, the other in the discal cell; the third cross-band is parallel with the second, of the same 
breadth, but longer, bordering the posterior cross-vein and terminating near the hind margin of the wing ; 
at its costal end the third band is united with the fourth, which forms a rather narrow border along the 
terminal portion of the costa and the tip of the wing to as far as the termination of the fourth vein. 
Hab. Mexico, Chilpancingo in Guerrero 4600 feet (H. H. Smith). 
A single male specimen. 
6. Rivellia flexuosa, sp.n., ¢. (Tab. X. fig. 13, wing.) 
Black ; front and antennx brownish ; tarsi rufous ; first cross-band broad, contiguous with the blackish base 
of the wing; third cross-band connected at the hind margin with the second and at the tip with the 
fourth band. 
Length 3°5 millim. 
