DIPTERA. 353 
The larve 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 pup, 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. ribesti; Scaeva 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 *. 
Baccna, 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 
(Sceva, Fab.) conopseus of Meigen, although the palette of the an- 
tenne is less orbicular than in Baccha +. 
We now pass to other subgenera, similar to the preceding ones, as 
to the form of the snout and the seta of the antennz, but in which 
the length of these organs is at least equal to that of the face of the 
head. 
‘Here, the antenne are not placed on a common pedicle, and their 
length does not surpass that of the head. 
Paracus, Lat., Meig.—Muuio, Fab. t 
Here, they arise from a common eminence, and are longer than 
the head. 
Sometimes the seta is lateral. 
SpHEcomyia, Lat., 
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., Meiq., 
Where the seta of the antenne 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 Chrysogaster, 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 antenne 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. 
+ Meig., Ibid. 
t See Latveille and Meigen. 
§ Idem. 
