DIPTERA. 335 



greenish-black, with thin white pollen. Tegulse large and thick, yellow, with brown tip, which bears a 

 very large and striking cluster of long reddish-brown cilia : these cilia show a tendency to stick together 

 and form a horn-like projection, as was remarked by Osten Sacken in describing P.Jlabellifer, and it is 

 not improbable that the cluster can be opened and closed by the insect in life. Abdomen green, the 

 posterior margin of the segments shining black, at the sides behind the incisures with some white pollen ; 

 hypopygium large, pedunculate ; the lamellae brown, paler at the base, with two prolongations, the dorsal 

 of which is small, the other long, slender, with a few long fine hairs on either side. Fore coxa? pale 

 yellow, middle and hind ones yellow, but infuscated on the outer side ; femora yellow, the hind knees 

 brownish ; tibia; yellow, the fore ones tipped with brown ; tarsi slender, black, with half or more of the 

 first joint yellow ; the middle tarsi bend sidewards between the second and third joints, which are 

 hollowed on the approximating sides, thus forming a grasping-organ (this can hardly serve any other 

 purpose than to hold the female); hind metatarsi shortened. Wings extremely long and narrow, 

 moderately and evenly infuscated ; costa with a very thick enlargement almost completely filling the 

 space before the first vein, this coming to a sudden end before the tip of the first vein ; fourth vein with 

 a gentle curve beyond the cross- vein, thence almost straight to the end of its course, which is just 

 before the apex of the wing. 



2 . Face white or greyish- white, ending in a sharp point somewhat below the eyes. Cilia of the tegulae of 

 ordinary size, black or faintly brownish. Wings wider, though but little shorter than in the male. 



Length 5-5, of the wing 7 millim. 



Hab. Mexico, Omilteme and Sierra de las Aguas Escondidas in Guerrero 7000-8000 

 feet (H H. Smith). 



Thirteen males and twelve females. Since the description was written, I have 

 captured specimens of this species at Hagerman, Idaho, U.S.A., about waterfalls. 



4. Polymedon triangularis, sp. n. 



S . Metallic green, somewhat dusted ; legs, including the fore coxae, yellow ; antennas, except the tip, also yellow. 

 Face silvery, rather narrow, projecting below the eyes more than its own greatest width; antennas of moderate 

 size, yellow,' the tip of the third joint infuscated ; front silvery-dusted, the green ground-colour showing 

 through a little when viewed from in front ; orbital cilia white, except a few directly above. Thorax 

 and abdomen green, on the sides dusted somewhat with white ; halteres and tegulse yellow, the cilia of 

 the latter indistinctly brown in colour. Hypopygium stout, black ; the lamellae small, triangular, cut off 

 square at the apex, on the dorsal side with a rounded emargination, yellow in colour but with a black 

 distal border. Middle and hind coxae quite black, except at the tip and on the inner side ; first joint of 

 fore and middle tarsi pale, except at the tip ; middle tarsi with a crook between the second and third 

 joints, the last part of the tarsus at this point seeming to bend sidewards to form a grasping-organ, as in 

 P. nimius, only not so strongly developed. Wings infuscated along the veins ; costa scarcely in the least 

 enlarged ; fourth vein very gently curved, ending considerably before the apex. 



Length 5 2 millim. 



Hab. Mexico, Cuernavaca in Morelos (H. II. Smith). 

 One male. 



[5. Polymedon superbus, 



Polymedon superbus, Aldrich, Trans. Ent. Soc. Lond. 1896, p. 318, t. 11. fig. 103, t. 12. figg. 113, 

 118, 119 l . 

 Hab. Antilles, St. Vincent 1 . 



This West-Indian species may be briefly referred to here. It differs from P. trian- 

 gularis in a few characters only ; but these are, in part, of the most permanent and 



