288 [Senate 



tlie 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 caliplera. 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 0j05. 



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 thoracica. 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 thoracica, 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 



