72 DIPTERA OF NORTH AMERICA. [PART III. 



B. Ovipositor flattened. 



a. Third antennal joint not circular. 



1. No prothoracic, no mesotboracic bristle. 



Section II, Platystomina. 



2. No pnothoracic, but a mesothoracic bristle. 



Section III. Cephalina. 



3. A prothoracic and a uiesothoracio bristle. 



Section IV. Ortalina. 



b. Third antennal joint circular. 



Section V. Pterocallina. 



DIVISION II. First longitudinal vein bare. 



A. Posterior angle of the anal 1 cell drawn out in a point, or, at least, 



more or less acute. 

 Femora n**ver armed. 



Section I. Ulidina. 



B. Posterior angle of the anal cell obtuse, rounded or retracted. 



Femora armed in most of the genera. 

 Section II. Richardina. 



FIRST DIVISION. 



ORTALID^E WITH THE FIRST LONGITUDINAL VEIN BRISTLY OR 

 DISTINCTLY HAIRY. 



First Section: PYRGOTINA. 



GEN. I. PYRGOTA WIED. 



Charact. Front of equal breadth, without ocelli, very much projecting in 

 profile. 



Antennae, drooping, second joint rather long, third more or less ovate ; 

 arista pubescent. 



Face retreating, under the antennae with deep fovese, separated by a 

 very low ridge ; they reach as far as the middle of the face, or only 

 a little below; lateral parts of the face very broad, still more 

 approximated on the lower half of the face; oral opening compara- 

 tively small ; clypeus but little developed ; proboscis not stout. 



Scutellum with many bristles. 



1 It may not be useless to refer here to Vol. I, p. xxiv, of these 3/b- 

 graphs, where (fig. 1) a wing of Orlalis is represented. The anal cell is 

 marked M on the figure, and is the same as the third basal cell, or the 

 posterior one of the small basal cells. Although this synonymy is not 

 mentioned in the explanation of the figure (at the foot of the same page), 

 it may be found in the same volume, p. xx, line 18 from the top. 0. S. 



