74 OHIO BIOLOGICAL SURVEY 



an obscure row of small tubercles, the posterior end has a long projection 

 one fourth its total length, the greater part of which is a dark glossy 

 brown. The ventral surface is flat and firmly attached to the leaf." 



Nathan Banks, Proc. Ent. Soc. Wash., V., 310, gives the following 

 on Ceria iviUistonii Yi'aX'A: "From a puparium collected on oak bark at 

 Falls Church, Va., about the middle of March, there issued March 27, a 

 fly of this species. It is probably identical with C. signifera Loew from 

 Mexico. The larva of Ceria is supposed to feed in the flowing sap of 

 trees. Puparium; dull black above, whitish below, in front with two 

 large white marks separated b}" a narrow black spot; anal tvibe shining 

 black. Dorsum faintly mottled with pale, more prominent on the sides. 

 Dorsum with a median row of double pointed tubercles, and a lateral row 

 each side; those toward the tip are .smaller than the others. lyCngth 

 18 mm." 



Eumerus —"The European E. strigatus has been bred from bulbs of 

 the common onion {^Alliiivi cepa) of which the}' sometimes destroj'ed a 

 whole crop. The larvae occurred in July and pupated in the bulbs or in 

 the neighboring earth. Sometimes bred from soft and rotten bulbs." 

 — Verrall. 



Part III. 



KEY TO THE GENERA OF SYRPHIDAE* 



1. Antennae with a terminal style (Fig. 152. s.) .... 2 



Antennae with a dorsal (rarely subterminal) arista (Fig. 151 ) 4 



2. Antennae cylindrical, the first two joints elongated; first posterior cell with a 



stump of a vein Ceria (p. 98) 



First two joints of the antennae short 3 



3. Eyes bare; small species Pelecocera (p. 88) 



Eyes pilose; larger species Callicera (p. 80) 



4. Marginal cell of the wings closed and petiolate (Fig. 231 ) 48 



Marginal cell open ( Fig. 151) 5 



5. Anterior cross-vein of the wings distinctly before (basal to) the middle of the 



discal cell; almost always rectangular ( Fig. 151 ) 6 



Anterior cross- vein near or beyond the middle of the discal cell, usually oblique 

 (Figs. 231, 246) 55 



6. Antennae elongate (Fig. 241; if arista plumose, see 56) 7 



Antennae short ( Fig. 240) 14 



7. Mesonotum with yellow lateral stripes; large species, the abdomen always with 



distinct yellow bands Chrysotoxum (p. 80) 



Mesonotum not with distinct yellow lateral stripes or margins 8 



8. Face rounded, not tuberculate, pilose; oral margin not projecting (Fig. 208).. . 9 

 Face not evenly arched ; tuberculate or the oral margin projecting (Fig. 37, 209) 12 



•After S. W. Williston. 



