62 DIPTERA OP NORTH AMERICA. [PART III. 



that of S. vau so closely that I have no hesitation in placing it 

 in the same genus. 



There are two other North American species which I take to 

 be undescribed, and which also belong to Stictocephala. As 

 their wings are not pictured like those of the two preceding spe- 

 cies, but simply banded, the difference between them seems, at 

 first glance, to be greater than it really is. A close examination 

 does not disclose any plastic difference which would justify their 

 generic separation from Stictocephala. I will describe them as 

 Stictocephala cribrum and cribellum. 



The North American species described by Macquart as Platy- 

 stoma annulipes shows, in the detail of its structure, an almost 

 complete agreement with the species of Stictocephala, but differs 

 so much in the outline of the wings and still more in the vena- 

 tion, that it cannot be placed in that genus. The difference in 

 the outline of the wings consists in the fact that the posterior 

 margin is more convex, and hence, the wings are broader ; the 

 difference in the venation appears in the posterior angle of the 

 anal cell being drawn out in a very long lobe, and in the position 

 of the posterior crossvein, the anterior end of which is much 

 nearer to the apex of the wing than the posterior end. As this 

 species does not find a convenient place in any of the existing 

 genera, I am compelled to establish a new one for it, which I call 

 CALLOPISTRIA. 



This would close the series of the few genera of Pterocallina, 

 hitherto sufficiently defined, if we had not to advert to the genus 

 PSAIROPTERA Wahlb., occurring in northern and central Europe, 

 as well as in northern Asia, a genus for which it is not easy to 

 find an appropriate place in the system. The species of this 

 genus resemble the Ulidina in their general appearance, and I 

 would not have hesitated to place them in that section, if their 

 third longitudinal vein was not distinctly beset with hairs. I 

 acknowledge that their location among the Ulidina is more 

 natural than among the Pterocallina. Nevertheless, I place 

 the genus among the latter and thus put a greater stress upon 

 the artificial character, derived from the pilosity of the third 

 vein, than upon more close and natural affinities, but which are 

 more difficult to explain in words. If I do this, it is because I 

 hold that a strict adherence to those characters, by means of 

 which I have tried to introduce into the systematic chaos of the 



