DIPTERA. 353 



The larvae feed exclusively on Aphides of all kinds, frequently 

 holding them in the air and soon exhausting them by suction. Their 

 body forms a sort of elongated cone, and is very uneven, or even 

 spinous. When about to become pupae, they fix themselves to leaves, 

 &c, with a kind of a glue. The body is shortened, and its anterior 

 portion, which was previously the most slender, then becomes the 

 thickest. 



S. ribesii; Scceva ribesii. Fab.; De Geer, Insect., VI, vi, 8. 

 Somewhat smaller than the Musca vomitoria ; head yellow ; 

 thorax bronzed, with yellow hairs ; scutellum of the same co- 

 lour; four yellow bands on the abdomen, the first interrupted*. 



Baccha, Meig.,Fab. 



Another subgenus closely allied to the preceding, only differing in 

 the abdomen, which is proportionally longer, narrowed at base, and 

 terminated in the manner of an elongated club. 



To this subgenus, in my opinion, should be referred the Syrphus 

 {Scceva, Fah.J conopseus of Meigen, although the palette of the an- 

 tennae is less orbicular than in Baccha f- 



We now pass to other subgenera, similar to the preceding ones, as 

 to the form of the snout and the seta of the antennae, but in which 

 the length of these organs is at least equal to that of the face of the 

 head. 



Here, the antennae are not placed on a common pedicle, and their 

 length does not surpass that of the head, 



Paeagus, Lat., Meig. — Mulio, Fab. % 

 Here, they arise from a common eminence, and are longer than 

 the head. 



Sometimes the seta is lateral. 



Sphecomyia, Lai.y 

 Where it is inserted on the second joint ; the last is much shorter 

 than the two others, than the first in particular, and almost ovoid ; 

 the latter and the second are long and cylindrical. 



I have established this subgenus on an Insect taken in Carolina by 

 the late M. Bosc. 



PsARUs, Lat., Fab., Meig., 

 Where the seta of the antennae is inserted on the back of the third 

 joint, near its extremity ; this joint almost borders on an oval, and is 

 nearly of equal length with the second : the first is much shorter. 

 The common peduncle is proportionally higher than in the analo- 

 gous subgenera. The wings are incumbent §. 



* Lat., Ibid. See Meigen. The Chrysorjast^-, Meig., appears to us to differ but 

 slightly from Syrphus ; the -wings are incumbent on the body, a character which 

 also belongs to several species of the preceding subgenus. The antenna; are almost 

 identical in both ; but in Chrysogaster the front of the females is canaliculated on 

 each side, the nasal eminence is larger, and forms a small rounded lump, with an 

 abrupt descent. 



f Meig., Ibid. 



X See Latreille and Meigen. 



§ Idem. 



