374 NORTH AMERICAN DIPTKRA. 



119. Sides of face at narrowest part less than one-third the width of 



the median depression (fig. 147). . . . Exorista. 

 Sides of face more than one-half the width of the median depres- 

 sion Metaphyto. 



1 20. Bend of fourth vein with a long appendage or distinct fold. 



Euphorocera. 

 Bend of fourth vein without such fold or appendage. Phorocera. 



121. First vein bristly except at tip and base. . . . Houghia. 

 First vein bare. ......... 122 



122. Facial ridges not bristly on more than lower half. . . 123 

 Facial ridges bristly on the lower two-thirds. Pseudochesta. 



123. Antennae reaching at least the lowest fourth of face. . 126 

 Antennae not reaching below lowest third. . . . 124 



124. Vibrissae less than one-half the length of the second antennal 



joint above oral margin. ...... 125 



Vibrissse at least the length of the second antennal joint above 

 oral margin (5) Acemyia. 



125. Third vein with a single bristle at its origin. . Comatacta. 

 Third vein bristly more than one-half the distance to anterior 



cross- vein Paraphyto. 



126. Lowest frontals below base of second antennal joint. . 129 

 Lowest frontal not below base of second antennal joint. . 127 



127. Facial depression without median carina. . . . 128 

 Facial depression with a carina; apical cell closed, the petiole 



twice the length of anterior cross-vein (8O, 81) . Euthera. 



128. Lower anterior corner of third antennal joint produced tooth- 



like (5) Acemyia. 



Antennae not so produced (44, 53) . . Vanderwulpia. 



129. Second abdominal segment without more than four marginal 



macrochaetae; or, if with more; the hind tibiae not ciliate. 130 



Second abdominal segment with at least six marginal macrochas- 



tae (4) Blepharipeza. 



130. Hind tibiae ciliated externally. ..... 131 



Hind tibiae not ciliated externally. ..... 135 



131. Facial ridges bristly almost to the middle. . . . 133 

 Facial ridges bristly on less than the lowest fourth. . 132 



132. Bristles of cheeks covering at least the lower two-thirds. Sturmia 

 Bristles of cheeks covering less than the lower half (94) . 



Hyphantrophaga. 



133. Frontals with at least three backwardly directed bristles in each 



row; abdomen largely or wholly opaque pollinose. . 134 

 With only two such bristles in each row; abdomen shining. 



Parachseta. 



134. With two or three backwardly curved bristles outside of the 



frontal rows Pseudochteta. 



Front without such macrochaetae (1O9) . . . Frontina . 



135. Bend of fourth vein without appendage. .... 137 

 Bend of fourth vein with appendage or distinct fold. . 136 



