334 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
THE THORAX. • 
Notum. 
This region of the body is more highly concentrated than in any other 
Phyloptera, not excepting the Trichoptera. The prothorax is a rather 
wide collar, longer and broader than in the Trichoptera, but the meso- 
thorax is spherical and very large in proportion to the metathorax, 
which is rudimentary and but slightly developed ; owing therefore to 
the large mesothorax and the small pro- and metatliorax, the entire 
thorax is oval-elliptical, and much consolidated, thus approaching in its 
general appearance the general shape of the Tipulid thorax, or that of 
the lower Lepidoptera. 
Pronotum. This forms a broad collar extending backwards on each 
side, the hinder edge being excavated in the middle. 
Mesonotum. This is long and well developed, not so wide as the body, 
the flanks extending out, when seen from above, beyond the sides of 
the notum. The prsescutum is well developed, forming a round, con- 
vex, swollen sclerite as long as broad, with a median suture-like im- 
pression. The scutum is very large and long, oval, about one-third 
longer than broad, slightly broader behind than in front. 
The scutellum is large and well developed, irregularly scutellatc in 
outline, with two bosses in front; the posterior end is narrow, truncate 
at the end, with the surface at the end somewhat swollen. 
Metanotum. The metathoracic segment is small, very short, and the 
notum and sternum, as also the pleurites, are somewhat rudimentary. 
The surface of the notum is somewhat depressed below T the level of the 
mesoscutellum. It is difficult to describe the sclerites. which are rep- 
resented in Fig. 1. The entire segment is about ono-tliird as long as 
broad. The scutum is not well differentiated, being represented by a 
median irregular area (Fig. 1 sc") about half as long as broad. No scu- 
tellum and postscutellum can be distinguished with certainty. 
Pleurum. 
The sclerites of the flanks are difficult to distinguish. In their de- 
velopment and arrangement the Ephemerina differ from all other Phy- 
loptera. 
Mesopleurum. Though there are a number of sclerites in the meso- 
thorax it is difficult to distinguish what are properly epistcrna and epi- 
rnera. The region of the mesepisteruum is indicated in Fig. 2 epis", 
and is much larger than the epiineral, which is the region situated over 
the insertion of the middle pair of legs. 
The first pair of spiracles is situated on the mesothorax under and 
in front of the insertion of the first pair of wings; the second pair is 
situated on the metathorax directly under the insertion of the second 
pair of wings. 
In the metaplcurum the episternal region is quite limited and minute 
compared with the large mesepisterual region j what I am inclined to 
