30 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser, 



white, the dorsal bristles black; four red bristles are inserted far apart near 

 the middle of the thorax, the outer pair being a short distance in front of 

 the insertion of the wings. Scutellum opaque gray, with four black bris- 

 tles. Abdomen metallic green, overlaid with a thick layer of gray dust, 

 bristles white. Hypopygium large and swollen, glabrous, black. Outer 

 appendages brownish yellow, rather large, but slender; inner appendages 

 pale yellow, very delicate, like dichotomously ramifying hairs. Penis very 

 slender, nearly straight. Pleurae dull metallic green, thickly dusted with 

 white. Bristles above the insertions of the fore coxae white. Coxae black, 

 piceous towards their tips, dusted with white and beset with white hairs. 

 Legs yellow, basal two-thirds of femora, trochanters, tips of tibiae and tarsi 

 from the tip of the first joint piceous. Hind metatarsus plain, second joint 

 two and two-thirds times as long as the metatarsus. Wings hyaline, with 

 brown veins which grow light yellow towards their bases. The costal and pos- 

 terior margins are parallel. Posterior cross-vein about as long as the distal 

 segment of the fifth vein, angular near its middle, to which is attached a 

 short but very distinct backwardly directed stump-vein. Third vein gently 

 but distinctly deflected downward and running a long distance parallel with 

 the fourth. The ends of these veins are rather far apart. Tegulae and hal- 

 teres yellow, the former with pale cilia. 



One specimen taken in sweepings on Lance Creek, in 

 Eastern Wyoming, August 14, 1895. 



The appendiculate structure of the posterior cross-vein, 

 so striking a feature of this species, is present in both wings 

 of the specimen. 



Thrypticus Gerstaecker. 



Mik's suggestion^ that my genus Aphantotimus^ is syn- 

 onymous with Gerstaecker's Thrypticus is well founded. 

 I believe this will also hold good of Aldrich's genus Xantho- 

 tricha} The three species described by Aldrich and the 

 two which I have described agree in presenting most of 

 the generic characters established by Gerstaecker on his 

 Thrypticus sm aragdin us . * 



The genus according to Kowarz^ "hat mit Medeterus 

 die meiste habituelle ^hnlichkeit, sie unterscheidet sich 

 von diesem durch den parallelen verlauf der dritten und 

 vierten Langsader." Other characteristics of the species 



1 Wien. Ent. Zeitschr, 1891. 



2 Psyche, July, 1890, pp. 375-377. 



3 Williston and Aldrich. Diptera of St. Vincent. Trans. Rnt. Soc. London, Pt. Ill, 1896. 

 * Uebersicht d. in d. Umgegend Berlins bis jetzt beobachteten Dolichopodiden, p.p. 



43-45- 

 5 Die Dipteren-Gattung Medeterus, p. 6. 



