FAMILY SYRPHID.E THE FLOWER FLIES 253 



Antennje shorter, if somewhat elongate they are decumbent and the 

 abdomen drooping or wholly black 19 



19. Face and scutellum more or less yellowish or translucent (if the face 



is entirely black the abdomen is oval and little more than twice as 



long as wide ) 20 



Face wholly black, the scutellum rarely with a yellow tip 38 



20. Abdomen drooping, never with yellow fasciae in American species 



though often largely reddish; third antennal segment more than 



twice as long as broad; ?mall species (7, 80) Paragus Latreille 



Abdomen not normally drooping; antennae usually short, the third seg- 

 ment rarely twice as long as wide, the abdomen usually with yellow 

 spots or bands 21 



21. Abdomen margined (the immediate latei"al margins raised and not 



cuiYing under ) ( 43 ) 22 



Abdomen not margined, the thin side margins curving under 27 



22. Species with long pile, the base of the abdomen broatUy pale yellowish, 



the abdomen moderately broad; eyes pilose (68, 81). 



Leucozona Schir.er 

 Species with shorter pile and usually with yellow markings beyond the 

 second segment 23 



23. Pleura with very bright, sharply limited yellow markings; front long 



and narrow Xanthogramma Schiner 



Pleura with diffuse yellowish markings or none; sides of mesonotum 

 sometimes yellow 24 



24. Third vein dipped into apical cell; third antennal segment long, robust, 



pointed; front not inflated; eyes bare; abdomen broad and flat, with 



wide fasciae Didea Macquart 



Third vein rarely dipped into apical cell, if so the eyes are pilose or 

 the abdominal spots are arcuate and the front more or less inflated. 25 



25. Male genitalia projecting, long and cylindrical; abdomen of female 



broadly oval, the fifth segment half as long as the fourth (84, 85). 



Eupeodes Osten Sacken 

 Male genitalia normal; if the fifth segment of the female is about 

 half as long as the fourth the abdomen has sub-parallel sides and 

 the front is not whitish yellow immediately above the antennae.... 26 



26. Wings practically without villi; front very much swollen; apical cell 



much broadened on the apical half (35, 86, 87) Scaeva Fabricius 



Wings largely villous; front seldom much swollen; apical cell witlened 

 in only a few species (9, 10, 32, 43, 47) *Syrphus Fabricius 



27. Pleura with sharply limited yellow markings; no yellow prescutellar 



spots; mesonotum without cinereous vitta; abdomen elliptical. 



Xanthogramma Schiner 

 Pleura with or without sharply limited yellow markings, if present 

 the abdomen is long and narrow or the mesonotum bears a cinerous 

 median vitta 28 



28. Abdomen dark except for a pair of large, basal yellowish spots; eyes 



pilose Ischyrosyrphus Bigot 



Abdomen differentlv marked; eves bare 29 



* Curran, 1930, Bull. Amer. Mus. Nat. Hist., Ixi, p. 56; Fluke, 1933, Trans. Wise. 

 Acad. Sci., Arts & Letters, 28, pp. 63-126. 



