196 Syrphidae. 



— Hind or all femora more or less black, front femora 

 without any dense, black ciliation behind 9. 



9. Front tibiæ and tarsi distinctly dilated; abdominal 



spots yelJow; balteres pale 10. 



— Front tibiæ and tarsi very slightly dilated ; abdominal 



spots hoary æneous ; balteres dark 11. sticticus. 



10. Middle pair of abdominal spots not much longer than 



broad; second and third joints on hind tarsi yellow 9. clypeatus. 



— Middle pair of abdominal spots about twice as long 

 as broad ; second and third joints on hind tarsi (gener- 

 ally) darkened 10. angustatus. 



F e m a 1 e s. 



1 . Antennæ quite black 2. 



— Antennæ pale beneath third joint 8. 



2. Lower part of epistoma with the central knob much 

 produced 3. 



— Epistoma rather flat, slightly or scarcely produced 4. 



3. Thorax dull ; mouth edge more produced than the 



central knob; anterior tibiæ and tarsi rather dark. . 1. manicafus. 



— Thorax shining ; mouth edge scarcely more produced 

 than the central knob; anterior tibiæ and tarsi much 



paler 2. tarsalis. 



4. Femora and tibiæ quite yellow ; sixth abdominal seg- 

 ment yellow 8. fidviventris. 



— Hind femora and tibiæ with blackish rings or at all 



events with traces of such 5. 



5. Hind femora and tibiæ with usually slight dark rings ; 

 - hairs behind front femora short and of equal length ; 



sixth abdominal segment quite or partly yellow 6. 



— Hind femora and tibiæ with usually more conspicuous 

 blackish rings ; hairs behind front femora longer and 

 increasing in length towards the base ; sixth abdominal 

 segment black 7. 



6. Front femora with no special white hair at the base; 

 basal abdominal spots large ; antennæ somewhat large, 



arista about as long as the antennæ 6. scambus. 



— Front femora with the special white hair at the base 

 present; basal abdominal spots smaller; antennæ 



shorter, arista not so long as the antennæ 7. immar ginatus. 



7. Not specially narrow species; frontal dust spots moder- 



ately large ; fifth abdominal segment with distinct spots 9. clypeatus. 



— Narrow species with abdomen pointed; frontal dust 



spots small; fifth abdominal segment without spots 10, angustatus. 



8. Abdominal spots bluish; frontal dust spots small; 



hind femora not or slightly pale at base 9. 



— Abdominal spots yellowish; frontal dust spots larger; 



hind femora with the basal part pale 10. 



9. Vertex about one third or fourth of the breadth of 



the head, shining; length 7—9 mm 5. albimanus. 



