-- 4 NORTH AMERICAN DIPTERA. 



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



the median depression (fig. 1471. . . . Exorista. 

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

 sion Metaphyto. 



120. 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 hristly except at tip and base. . . . Houghia. 

 First vein bare I22 



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

 Facial ridges bristly on" the lower two-thirds. Pseudochseta. 



123. Antenna; reaching at least the lowest fourth of face. . 126 

 Antennae not reaching below lowest third. . . . 124 



124. Vibrissge less than one-half the length of the second antenna! 



joint above oral margin 125 



Vibrissa at least the length of the second antenna! 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 (80, 81 1 . Euthera. 

 128 Lower anterior corner of third antennal joint produced tooth- 

 like (5) Acemyia. 



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



129. Second abdominal segment without more than four marginal 



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



Second abdominal segment with at least six marginal macroclue- 



t£e (4) Blepharipeza. 



130. Hind tibis ciliated externally. 13 1 



Hind tibiae not ciliated externally r 35 



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

 Facia! 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 backwanllv directed bristles in each 



row; abdomen largely or wholly opaque pollinose. . 134 



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



Parachseta. 



1 }4. With two or three backwanllv curved bristles outside ot the 

 frontal rows Pseudoctueta. 



Front without such macrocb^etse (109) . . ■ Frontina. 

 135. Bend of fourth vein without appendage '37 



bend of fourth vein with appendage or distinct fold. . I36 



