SYRPH-IDAE OF MAINE. 257 



I. THE APHIDOPHAGOUS TYPE 



Key to Species 



Dorsal pair of slit-like spiracles much shorter than the other pairs, 



its carina rounded. Larvae phytophagous 



Toxomerus politus, p. 216. 



All the slit-like spiracles elongate, at least several times as long as 

 broad, or at least the dorsal pair not conspicuously shorter. 

 Larvae aphidophagous 2 



Posterior slit-like spiracles greatly elongate and extensively sin- 

 uate or undulate. (Fig. 34-j) Syrphus nitens, p. 242. 



Posterior slit-like spiracles straight or somewhat curved, never 

 much • sinuate 3 



General color greenish, with white longitudinal stripes. Rather 

 smooth-bodied larvae with no integumental vestiture and the 

 segmental spines not prominent 4 



General color yellowish, reddish or brownish 6 



Posterior respiratory organ less than half as long as broad.. Slit- 

 like spiracles less than twice as long as broad. Viscera usually 



plainly visible thru the skin. (Fig. 30-5 and 6) 



Melanostoma mellinum, p. 226. 



Posterior respiratory organ considerably longer than broad. Slit- 

 like spiracles each at least three times as long as broad.. 5 



Stigmal plates roughened, the spiracles well elevated and separated 

 by spur-like elevations. The two tubes very slightly .divergent 



at the tip. (Fig. 31-66 and 68) , 



Atflograpta obliqua, p. 234. 



End of posterior respiratory appendage nicely rounded off, smooth, 

 the spiracles not elevated, and not separated by perceptible 

 spurs. The two tubes not at all divergent. (Fig. 31-7-? and 73). 

 Sphaerophoria cylindrica, p. 231. 



Integument of the larva bare except for the segmental spines 7 



The entire dorsal surface of the larva covered with short, micro- 

 scopic spines, black, or sometimes light in color and then not 

 prominent 8 



Posterior respiratory appendage longer than broad ; inter-spirac- 



ular nodules rather prominent 



Syrphus xanthostomus (34, p. 81 ) . 



Posterior respiratory appendage broader than long; inter-spirac- 



ular nodules not prominent. (Fig 33-13) 



Syrphus torvus, p. 240. 



Segmental spines conspicuous or raised on prominent, fleshy or 

 spiny, conical elevations easily seen by the naked eye 9 



Segmental , spines not prominent and not raised on conspicuous, 

 conical projections; sometimes hard to distinguish from the 

 integumental spines „,.... 11 



