SYNOPSIS OF NORTH AMERICAN SYRPHID^. 67 



5. — The width of the front iu the female nearly equal to half its length . pauxillus 

 The width above distinctly less than half the length (see ?oi«8, var.) .... 



6. — Eastern species amalopis 



Western species intrudens 



7. — Front in female broad ; the abdominal spots, as a rule, do not reach the margin ; 

 hind metatarsi of male distinctly swollen; face projecting below . contumax 



Front in female not unusually broad 8 



8. — Third antennal joint scarcely longer than broad; face with an indistinct black 

 stripe; second and third abdominal spots do not reach the lateral margin; 



the first pair not broader sodalis 



Third antennal joint considerably longer than broad ; face with a distinct black 



stripe ; abdominal spots narrow mentalis 



Third antennal joint oval ; first pair of abdominal sjiots very large; eyes thickly 



pilose velutinus 



9. — Abdominal spots of third and fourth segments distinctly arcuated . arcuatus 



Abdominal spots straight, transverse 10 



10. — Face unusually projecting below, the distance from vertex to antennto scarcely 



greater than from thence to tip of tubercle geniculatus 



Face not unusually projecting below 11 



11. — Face with a blackish stripe; all the abdominal spots of nearly equal width 



umbellatarum 

 Face wholly without a blackish stripe ; first pair of abdominal spots small, sec- 

 ond and third pairs large, nearly square disjectus 



12. — Abdomen narrow, with nearly parallel sides in the male ; in the female, the fifth 



segment half as long as the fourth diversipes 



Abdomen distinctly oval ; the fifth segment in the female less than half as long 



as the fourth 13 



13. — Femora black at the base 14 



Femora yellow at the base 20 



14. — The second and third abdominal cross-bands do not reach the lateral margin 15 



The second and third bands reach the margin 18 



15. — Eyes bare 16 



Eyes pubescent; the spots on the second segment separated from the lateral 

 margin ; the second and third bands bilaterally oblique .... lotus 

 16. — Spots on second segment not reaching the lateral margin ; cheeks black, 



americanus 

 The band or spots on second segment attains the lateral margin .... 17 



17.— Cheeks black abbreviatus <? 



Cheeks yellow opinator 



18.— Eyes pubescent torvus 



Eyes bare 19 



19. — The cross-bands attenuated at their ends ribesii 



Cross-bands reach the sides in nearly their full width Lesueurii 



20. — The second and third abdominal cross-bands attain the lateral margin . . 21 



The second and third bands not quite reach the margin * . . 23 



21. — The second and third cross-bands attenuated at their tips ; face and cheeks yellow, 



protritus S , $ 



ribesii ^ 



Second and third cross-bands not distinctly narrowed at their ends ... 22 



22. — Face and cheeks wholly yellow; abdominal bands broad . . xanthostomus 



Face with a median stripe and the cheeks black ; abdominal band narrow, 



genualis 

 23.— Cheeks black ; the first pair of abdominal spots narrowly separated from the 



margin americanus 



Cheeks wholly yellow ; the first pair of abdominal spots reach quite to the edge 



opinator 



