376 



NORTH AMERICAN DIPTERA. 



154. Head at vibrissae as long as at base of antennae. . . 155 

 Head at vibrissae much shorter than at base of antennae. 157 



155. Posterior cross-vein much nearer to bend of fourth vein than to 



the anterior cross-vein. . . . . . . 156 



Posterior cross-vein at most only slightly nearer to bend of fourth 

 vein than to anterior cross-vein. . . . Trichogena. 



156. Fifth vein not reaching the hind margin (39, 61) . 



Elachipalpus. 

 Fifth vein reaching the hind margin. . Brachycoma. 



157. Facial ridges almost parallel; sides of face at narrowest part 



nearly as wide as the median depression. . . . 158 

 Facial ridges widely diverging below; sides of face less than one- 

 half as wide as median depression. .... 159 



158. Fifth vein not reaching the wing margin (39, 61) . 



Elachipalpus. 

 Fifth vein reaching the wing margin (GO) . . Opsidia. 



159. Fifth vein not reaching the wing margin (39, 61) . 



Elachipalpus. 

 Fifth vein reaching the wing margin (88). . Metopia. 



160. Head at vibrissae much shorter than at root of antennae. 



Hilarella. 

 Head at vibrissae as long as at root of antennae. Brachycoma. 



1 6 1. Head at vibrissae much shorter than at root of antennae. 162 

 Head at vibrissae as long or longer than at root of antennae. 168 



192. Eyes distinctly hairy. . . . . . . . 163 



Eyes bare or with very short hairs. . . . . . 164 



163. Facial ridges not bristly on more than lowest fifth; antennae of 



male divided longitudinally (1O3, 104). Dichocera. 



Facial ridges bristly on at least the lower half (111) . Gaediopsis. 



164. Ocellar bristles wanting (99). . . . Microphthalmia. 

 Ocellar bristles present. . . . . . . . 169 



165. Ocellar bristles directed backward, robust. . . . 166 

 Ocellar bristles directed forward. . . . . . 167 



166. Front opaque, the vitta deep brown or black (3) . Spallan^ania. 

 Front shining, the vitta light yellow (12, 13). . Gonia. 



167. Frontal ridges bristly on less than the lowest fourth (99). 



Microphthalmia. 

 Frontal ridges bristly on at least the lower half (87) . 



Chaetog-asclia. 



168. Palpi absent or vestigial. ....... 169 



Palpi well developed. . . , . -.175 



169. With one or more stout macrochaetae on either side near lower 



end of eye. . . . . . . . . . 172 



Without such macrochaetae. . . . . . . 170 



170. Abdomen with discal macrochaetae. . . . . . 171 



Abdomen without discal macrochaetae. . . Gymnomma. 



171. One discal and one marginal pair of macrochaetae on second ab- 



dominal segment. ..... Parepalpus. 



