MODIFICATIONS OF THORAX 59 
the episternum in front of the wing process. The third (3P,), lying behind 
the wing process, is well developed. 
The mesosternum is hard to define in the mosquito. A pentagonal sternal 
plate lies between the mesocoxal cavities behind the median ventral extension 
from the episterna already described. The postcoxal plates (S,) of the meso- 
thorax are attached to the posterior parts of its sides, while its posterior angles 
are prolonged into slender bands that extend outward and upward in front of 
the metacoxze and become continuous with the lower parts (c) of the metapleura. 
Hence, this plate would appear to represent both the mesosternum and the 
metasternum, for otherwise there is no metasternal element. 
The Metathorax.—The third segment of the thorax is difficult to describe. It 
is not only reduced in size, but the typical structure is so obscured by secondary 
modifications that it is impossible to say, from a morphological standpoint, what 
some of the parts are. The tergum (7',) forms a narrow dorsal bridge between 
the postnotum (PN,) of the mesotergum and the first abdominal tergum (I7') 
The upper part of the pleurum carries the halter (W,) the representative of the 
hind wing. An irregular line (PS,) extends downward from the wing support 
(WP,), which may be known, by the corresponding internal ridge, to be the 
pleural suture, but it divides before it reaches the coxa and incloses an elongate 
area (c) that carries the coxal articulation. The plate (Hps,) in front of this 
suture is, of course, the episternum, while at least some part of the surface be- 
hind it must be the epimerum (Hpm,). The structure of this part, however, is 
so broken up by accessory sutures that the limits of this sclerite can not be posi- 
tively asserted. The ventral pleural plate (c) is anomalous and may represent 
the lower parts of both the episternum and the epimerum since it bears the ar- 
ticulation of the metacoxa (Cz,). It is connected by a precoxal band with the 
pentagonal sternal plate, as described under the mesothorax. Behind the epi- 
merum (Hpm,) are two plates (PN,) reflected upon and fused with the an- 
terior edge of the first abdominal tergum (IT). A study of other Diptera sug- 
gests that these two plates together represent the postnotum (postscutellum) of 
the metathorax, though, on the other hand, they may belong to the first abdom- 
inal segment. 
The second spiracle is almost surrounded by the metaepisternum, an unusual 
condition, though it is generally conceded to belong to the metathorax. 
To the preceding discussion of the thoracic structures by Mr. Snodgrass but 
little need be added. The thorax is remarkably uniform in structure within the 
Culicide and but few modifications occur that are of systematic value. In the 
systematic part of this work we call the most prominent parts of the prothorax, 
considered by Snodgrass as probably tergal, the prothoracic lobes. These lobes 
show considerable diversity in different genera. In most of the Culicini the pro- 
thoracic lobes are small and lateral. In the genus Stegoconops, however, they 
are large and very prominent, and nearly contiguous upon the dorsum. In the 
Sabethini a few genera have the lateral lobes well separated but rather promi- 
nent laterally (Joblotia, Lesticocampa, Prosopolepis). In most sabethids, 
however, the prothoracic lobes are large and prominent, contiguous or nearly so, 
