288 [Senate 
the exterior margin. The two species may at once be discriminated 
from each other by observing the space about the apex of the anal 
nerve ; this is perfectly hyaline in the wheat-fly, and clouded in the 
species under consideration, to which the following name and essen¬ 
tial marks may be assigned : 
Cecidomyia caliptera. Orange-red; tarsi whitish to their tips; wings hyaline, with 
seven dusky spots, three based on the inner margin, the middle one being on the apex 
of the anal nerve. 
Length 0.05. 
A few specimens occurred to my notice about the middle of the 
month of August, having the abdomen more tinged with red than in 
the wheat-flies, but commonly fading, when preserved, to a flesh- 
color or dull yellow; the thorax brown or blackish above, its sides 
dull yellow ; legs blackish except at their bases, and poisers of the 
same hue ; wings dusky, with their nervures more distinctly marked 
than in the wheat-flies. I would propose for this species a name 
alluding to the contrast between the color of the thorax and of the 
abdomen, in a dorsal view of the insect (Plate, fig. 8). 
Cecidomyia tlioracica. Red: thorax above blackish-brown: legs and poisers blackish: 
wings dusky. 
Length 0.05. 
A much more abundant species, and very closely related to the 
preceding, occurs from the last of July till the middle of September, 
and perhaps later. Its legs are dusky, but not of so deep a tint as 
those of the thoraQica, from which, moreover, it is readily distin¬ 
guished by having invariably a fulvous-brown or blackish spot at 
the base of the abdomen on its upper side. The base and sides of 
the thorax are of the same color with the abdomen, namely, red, or 
in old specimens dull pale yellow; the upper side, forward of the 
scutel, being brown. This species (Plate, fig. 5), may be named 
and characterized as follows: 
Cecidomyia tergata . Red: thorax anteriorly and spot at base of tergum brown: wings, 
legs and poisers dusky. 
Length about 0.06. 
Each of the preceding appear to be quite distinct from any of the 
European species that have been described. 
The history of the insect which has now been considered, presents 
some very singular and deeply interesting traits. Far back in the 
vista of years we see it a powerful depredator: anon it sinks into 
