248 8. W. WILLISTON, M. D. 



a.— Front Bud face narrow, of equal width, front nearly uniformly convex in 

 profile. 

 b. — Front and face wholly yellow. 



c. — Antennse short, but little longer than the face ; face and front with 

 long, blackish pile; wings not conspicuously spotted. Two speci- 

 mens, Eio. 

 cc. — Antennae elongate, about half the length of the front; front and face 

 not markedly pilose. 

 d. — Pleurse and pectus wholly yellow ; outer end of hind femora brown. 

 One specimen, Eio. 

 dd. — Pleurse with a black spot, pectus yellow ; hiud femora wholly reddish 

 yellow. One specimen, Eio. 

 ddd. — Pleurse with large black spot, pectus broadly black. Three speci- 

 mens, Eio. 

 hb. — Front with a brown stripe, otherwise like ddd. One specimen, Eio. 

 aa. — Face rather broad above, the sides gently divergent to oral margin ; front 

 ^distinctly concave on lower two-thirds,, and with a broad black 

 stripe not reaching the antennsB ; median dorsal stripe deep black 

 to prothorax ; wings broader, the stigmatic and distal infuscatious 

 more pronounced, and all the veins on the posterior border 

 clouded. Four specimens, Chapada. 



Accepting Macquart's deterniiiiation, we may call the short an- 

 teniiied specimen C. vespertiilo, and the specimens from Chai)ada, 

 with the frontal stripe, and the frontal gibbosity above, C. cadanen 

 Macquart, but these are only guesses. I have seen specimens very 

 closely allied, from Tehuantepec, and Bigot has described also a spe- 

 cies that cannot be distinguished, from the West Indies. It is prob- 

 able that the species have a wide distribution. To name new species 

 in such genera, without the study of considerable material, or at least 

 without pointing out differences from the previously described ones, 

 is highly reprehensible. 



9. Cacosis nigra Wiedemann, Auss. Ins. ii, 28 (Sargus) ; Walker, Dipt. 



Saund. pi. iii, fig. 1 ; Schiner, Novara Exped. 67. — Brazil. 



One specimen, Rio de Janeiro, November. Wiedemann's descrip- 

 tion applies excellently well, except as corrected by Schiner. 



10. Ptecticus aOinis Schiner, Novara Exped. 65. — S. America. 



Five specimens, Chapada, November, December. The fifth seg- 

 ment has a narrow, black, or blackish transverse spot, and I see no 

 transverse " Biindchen" on the front; otherwise the specimens agree 

 with the description. 



11. ^iargus thoraciciis Macquart, Hist. Nat. Dipt, i, 260. — S. America. 

 One specimen, Chapada. This specimen I should have referred to 



S. concinmis O. S., described from a male specimen from Mexico and 



