372 NORTH AMERICAN DIPTERA. 



84. Cheeks about one-fourth or less of eye-height (97, 98) . 



Plagiprospherysa. 

 Cheeks nearly as broad as eye-height. . . Baumhaueria. 



85. Eyes bare, or with indistinct hairs. ..... 86 



Eyes distinctly hairy Cyrtophloeba. 



86. Sides of face without stout niacrochsetae. .... 87 

 Sides of face with one or more pairs of niacroclnette. Paraplagia. 



87. Arista thickejied almost to its tip; third vein bristly nearly to an- 



terior cross-vein. ...... Metaplagia. 



Arista not thickened to the middle; third vein bristly less than 

 half way to the cross-vein (62). . . Heteropterina. 



88. Sides of face bare on lower half. ...... 89 



Sides of face with hairs. 140 



89. Vibrissa; distinctly alx>ve oral margin. .... 91 



Vibrissas on a level with oral margin. ..... 115 



Vibrissa; very vestigial. ....... 90 



90. Wings nearly wholly brownish black; black species (58, 59). 



Penthosia. 

 Wings brownish anteriorly only. . . . Clinogaster. 



91. Eyes bare. .......... 92 



Eyes hairy. .......... 109 



92. Penultimate joint of arista more than twice as long as broad. 93 

 Penultimate shorter or only slightly longer than broad. . 94 



93. Proboscis beyond basal articulation at most one and two fifths 



times the height of head (2). . . . .. Aphria. 



Proboscis beyond basal articulation at least two and one-third 

 times the height of head (114). . . Chaetoglossa. 



94. Palpi absent or vestigial (54). .... Ocyptera. 

 Palpi present. ......... 95 



95. Proboscis beyond basal articulation at least one and one-third 



times the height of head (2). ..... Aphria. 



Proboscis beyond basal articulation at most one and one-fifth times 

 the height of head 96 



96. Antenna; reaching at least the lowest fourth of face. . . 105 

 Antenna; not reaching below the lowest third. ... 97 



97. Vibrissa; at less than half the length of the second antenna! joint 



above the oral margin. ....... 98 



Vibrissa: at least the length of the second joint above the oral 

 margin. .......... 99 



98. Lowest frontal bristles not below the base of the second antenna! 



joint (72, 75) Pachyophthalmus. 



Lowest frontals below the middle of second antenna! joint (6). 



Atacta. 



99. Lowest frontals below middle of second antenna! joint. . 100 

 Lowest frontals not below middle of second joint. . . 103 



100 Ocellar bristles directed forward. ...... 101 



Ocellar bristles wanting. ..... Belvosia. 



