376 



NORTH AMERICAN IHPTKRA. 



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



Head at vibrissa; 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. ...... J56 



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 (90). . Opsidia. 



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



Elachipalpus. 

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



160. Head at vibrissa? much shorter than at root of antenmu. 



Hilarella. 

 Head at vibrissae as long as at root of antenna;. Brachycoma. 



161. Head at vibrissa; much shorter than at root of antenna;. 162 

 Head at vibrissa? as long or longer than at root of antennae. 1 > 8 



192. Eyes distinctly hairy. '63 



Eyes bare or with very short hairs. . . .' . . 1^4 



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



male divided longitudinally (103, 10 4). Dichocera. 



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



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

 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) . Spallanzania. 

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



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



Microphthalmia. 

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



Chaetogaedia. 



168. Palpi absent or vestigial > (, 4 



Palpi well developed. . . , • • 175 



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



end of eye. ......... '7 2 



Without such macroclneta;. 17° 



170. Abdomen with discal macrochaetae 17* 



Abdomen without discal macrochaetae. . . Gymncmma. 



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



dominal segment Parepalpus. 



