66 DIPTERA OF NORTH AMERICA. [PART III. 



Second Section: Richardina. 



Among all the genera of this group, Richardia Rob. Desv., 

 distinguished by its posterior femoi'a, armed with spines, is the 

 best and longest known. This circumstance induced me to 

 derive the name of the section from it. It seems to be exclusively 

 American ; the Richardia favitarsis Macq., from the Marquesas 

 Islands, does not belong to this genus, and if the manner in which 

 the auxiliary vein is represented upon Macquart's figure be only 

 of average correctness, we may even infer that it does not belong 

 to the Richardina at all. The other species which Macquart, 

 Rondani and Gerstaecker have added to the genus Richardia are 

 all natives of America. The two males of Richardia described 

 by Gerstaecker are distinguished by the dilatation of their head, 

 somewhat in the manner of Achias ; their females are not known 

 yet; still the analogy of Achias and of other genera, having a 

 similar structure of the head, justifies us in supposing that their 

 heads do not show any extraordinary dilatation. 



The fly of unknown habitat which Macquart described as 

 Odontomera ferruginea undoubtedly belongs in the immediate 

 affinity of Richardia. As I have never seen it, my knowledge 

 of it is based exclusively upon Mr. Macquart's statements. 

 These, however, are entirely sufficient to prove that the fly 

 belongs in the family Ortalidse, and not in the Trypetidse, where 

 Macquart places it. That it belongs to the Richardina I infer 

 from the evidently very close relationship which exists between 

 it and the Sepsis Guerinii Bigot from Cuba. The generic name 

 must be changed, on account of the already existing Odontomerus 

 Gravenh. 



This Sepsis Guerinii agrees in so many characters with Odon- 

 tomera ferruginea Macq. that one might be tempted to place it 

 in the genus Odontomera. Should Macquart's statements, how- 

 ever, be correct, this would not be admissible, as Odontomera 

 ferruginea possesses not only much stouter femora and a much 

 more projecting front, but also an auxiliary vein which is much 

 less approximated to the first longitudinal than in Sepsis 

 Guerinii. We are compelled, therefore, to consider Sepsis 

 Guerinii as a separate genus of the Richardina, which we will 

 call Stenomacra. 



We have, in the next place, to mention the genus Setellia. 



