52 DIPTERA OF NORTH AMERICA. [PART III. 



adopted for Ortalis marginata Say, for which I propose the name 

 of Idana. 



Diacrita is easily distinguished from Idana by the shape of 

 the posterior angle of the anal cell, which is drawn out in a very 

 long lobe, and by the picture of the wings, which consists only 

 in a very broad dark border, extending to the very apex of the 

 wing. The more extended picture on the wings of Idana is not 

 unlike that of Pteropoecila and the posterior end of its anal cell 

 forms only a short angle. As both genera contain North American 

 species, I will have occasion to refer to them again more in detail. 



Fourth Section: Ortalina. 



The Ortalina have a prothoracic, as well as a mesothoracic 

 bristle, while among the Cephalina, the former, among the Pla- 

 tystomina, both are wanting. The Ortalina are also distinguished 

 from the two above-named groups by a smaller oral opening, a 

 less developed clypeus, a less stout proboscis, a less turgid 

 mentum and smaller palpi. In seveual genera, moreover, the 

 thoracic dorsum is beset with bristles as far as its anterior 

 portion. The abdomen of the female has five segments, which 

 brings this group nearer to the Cephalina than to the Platysto- 

 mina. 



The geographical distribution of the Ortalina is, as far as 

 known, confined exclusively to America and to Europe, with 

 those parts of Asia which belong to the faunal province of the 

 latter. Yery striking is the great agreement between the 

 European and North American forms of this group. As the 

 knowledge of the latter is still very fragmentary, the generic 

 distribution of the probably numerous species which may be 

 discovered yet would offer great difficulties, or lead into error, 

 unless based upon the knowledge of the European genera. I 

 will give here, for this reason, a review of all the European 

 genera adopted at present. Besides these, however, to the 

 Ortalina must be reckoned the genus Apospasmica, which I 

 propose to establish for the South American Ortalis fasciata 

 Wied. and the genus Automola, which I have adopted above for 

 Ortalis irifasciata Wied. and atomaria Wied. 



The European genera of Ortalina are the following: — 





