40 



UNITED STATES NATIONAL MUSEUM BULLETIN 224 



exceptionally fine and unusually long and erect, this 

 pile longer and somewhat more conspicuous on the 

 posterior third of the mesonotum, and with a rather 

 conspicuous patch of similar, equally long pile on each 

 side of the disc of the scutellum which is also black in 

 color. Ventral margin of scutellum, upper mesopleu- 

 ron and propleuron with abundant, long, fine, white 

 hairs. Metapleuron with a vertical band of some 20 

 similar bristly hairs. 



Legs: The legs are slender; anterior femur with the 

 basal half and middle femur with the basal fifth shin- 

 ing blackish, the color diffusely delimited. Apex of 

 the first four tibiae narrowly black and all the basal 

 segments quite black. Remainder of these tibiae and 

 their femora light orange brown. Hind legs missing. 

 Pile of the middle femur quite fine and erect, chiefly 

 pale and long ventrally, but with a few quite long, black 

 hairs intermixed and with some short, black hairs dor- 

 sally on the outer third, besides 1 or 2 slender, black, 

 dorsal and apical bristles. Middle tibia with 7 oblique, 

 long, quite slender, black bristles and 4 still longer, 

 stouter, pale yellow, anterodorsal bristles ; 5 posterior 

 yellow hairs that are long and bristly; 2 long, stout, 

 posteroventral, yellow bristles; and 1 similar, basal, 

 anteroventral bristle. Anterior femora with quite abun- 

 dant, long, exceptionally fine, erect, blackish hairs from 

 the dorsal, posterior, and ventral surfaces and also with 

 abundant but rather short, fine, yellow hairs medially. 

 Anterior tibia with the bristles short, except for 2 long, 

 rather thick, yellow, posteroventral bristles and beyond 

 them a single long, black, bristly hair and posterodor- 

 sally 7 short, rather stout, black bristles and 8 similar, 

 anterodorsal, short, black bristles. Ventral surface with 

 numerous, very fine, erect, black hairs, which are both 

 short and long. Bristles at the apices of the tibiae 

 chiefly yellow. Claws slender, pulvilli long and spatu- 

 late. Empodium quite stout at the base and pale in 

 color. 



Wings: The wings are hyaline; the veins dark sepia- 

 brown, except basal to the humeral crossvein they are 

 light orange-brown. 



Abdomen: The abdomen is more or less compressed, 

 shining black with a faint greenish to brassy luster 

 similar to Broticosia rapax Hull but less pronounced. 

 The sides of the tergites are rather densely covered with 

 a remarkably fine, minute, pollenlike, whitish bloom 

 or micropubescence. Pile erect, fine and yellow; es- 

 pecially dense and long on the sides of the first 3 ter- 

 gites, shorter in character dorsomedially and greatly 

 reduced beyond the third tergite. Sternites with long, 

 fine, erect pile which is mostly yellow but with some 

 black hairs intermixed. Terminalia shining black, the 

 proctiger basally and laterally reddish brown. 



Type: Male, Dubbo, New South Wales, August 29, 

 1925. In the collection of Commonwealth Scientific 

 and Industrial Research Organization, Canberra, 

 A.C.T. 



Genus Leptarthriis Stephens 



Figukes 4, 411, 807, 816, 1895, 1898 



Leptarthrus Stephens, Syst. Cat. British Insects, pt. 2, p. 258, 

 1829. Catalog name accompanied by unnamed figure and 

 definitive hind tarsus of a male fly. Type of genus : 

 Dioctrla brevirostris Meigen, 1804. Taken from Verrall 

 (1909). 



Isopoyon Loew, Linnaea Entomologica, vol. 2, p. 492, 1847. 

 Type of genus : Dioctria brevirostris Meigen, 1804, by mono- 

 typy. 



Small flies, characterized by a rather robust abdomen, 

 tapered at the apex only. They have short, appressed 

 pile with dense, long pile of the head and mesonotum. 

 The mesonotum is high, and the face wide with paral- 

 lel sides. These flies are distinguished in the male by 

 the curious swordlike, thin, and laterally compressed 

 hind basitarsus, and in the female by the slender, elon- 

 gate, simple ovipositor formed from the narrow, tube- 

 like sixth to eighth segments. Length 10 mm. 



Head, lateral aspect: Face low and gently rounded, 

 slightly produced beneath the antenna and protruding 

 but little more on the lower face. Eyes strongly con- 

 vex anteriorly, gently behind, without ventral reces- 

 sion. Occiput prominent, moderately developed, thin- 

 ning at vertex and again at the bottom of the eye. 

 Occiput without bristles but with uniformly dense, 

 long, crinkled, delicate pile ; the long pile begins some 

 distance from the eye margin. Proboscis small, short, 

 oblique, obtuse, strongly swollen towards the base and 

 from dorsal view acutely triangular. It has a low 

 medial ridge and short stiff pile at the apex and in the 

 middle laterally ; at the base below are numerous long, 

 fine hairs. Palpus distinctly of 2 segments, the first 

 segment longer, robust, with numerous fine long hairs 

 laterally and stiff pile below. The short, apical seg- 

 ment is porate and bears just beyond its middle a crease 

 which may indicate a subdivision and bears a few long 

 slender hairs. Antenna attached just above the mid- 

 dle of the head. The first 2 segments are short, bead- 

 like, and equal in length. The third segment is rather 

 long, slender, tapered from the middle to the apex and 

 bears 2 microsegments, the first quite short, the second 

 3 or 4 times as long, with at its apex a distinct spine. 

 The microsegments and third segment thickly pilose, 

 the former held at a distinct oblique angle. First 2 

 antennal segments with several long stiff hairs dor- 

 sally, the first segment ventrally and laterally with 8 

 or more long, slender, bristly hairs, the second segment 

 with 2 or 3 hairs. 



Head, anterior aspect : Face wide, a little more than 

 one- fourth of head width and slightly divergent below. 

 Face pubescent or sometimes bare in the middle and 

 bearing numerous, long, curved, stiff pile or bristly 

 hairs. These bristly elements extend nearly to the an- 

 tenna and are largely directed forward; the lower 

 elements are more numerous and curled downward. 

 Subepistoma small, concave and not quite horizontal. 

 The front is short, very slightly divergent, the vertex 

 of the same width. The front bears a number of slen- 



