220 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
is movably connected with the succeeding middle or mesothoraxf 
which bears the second pair of legs and a pair of long narrow 
wing-covers or tegmina (singular legmen) above; this segment is 
rigidly joined to the hind or metathorax, which bears the large 
hind legs and the broad, black, membranous wings. 
The three thoracic segments are believed to present the same 
plan of structure greatly modified in details. The ventral face 
of each is stiffened by a single sclerite, the sternum. On each side 
are two pleural sclerites, the episternum and epimeron. Each 
dorsum, tergum, or notum is composed of four sclerites arranged in 
a longitudinal series and named from before backward the prae- 
scutum, scutum, scutellum, and post-scuteUum. To these terms 
are attached prefixes pro-, meso-, and meta-, to indicate the 
particular segment, e. g., the metepisternum is the episternum of 
the metathorax. 
The prothorax consists principally of a large dorsal piece, the 
pronotum, which in many Locusts and Grasshoppers is saddle- 
shaped, but which in this species and some of its allies bears a 
high median ridge (mid-carina) cut deeply in front of the middle 
by a groove, sinus, or sulcus which extends downward nearly to 
the ventral edge of the pronotum. This is the principal sidcus 
and it lies between the third and fourth dorsal sclerites (scutellum 
and post-scutellum) of the prothorax. That part of the prono- 
tum in front of it is termed the prozona or prozone, behind it the 
metazona or metazone. About on a level with the points of 
attachment of the wing-covers and running forward will be found 
the low, dull lateral carinae, in this species interrupted in the 
middle but usually very distinct in the Slant-faced Locusts 
(Tryxalinae = Acridinae of this Manual). These separate the 
top or disk of the pronotum from the sides or lateral lobes. By 
close scrutiny other sutures may be seen in addition to the prin- 
cipal sulcus, extending for the most part dorso-ventrally and 
indistinctly indicating the other scleritts of which the pronotum 
is made up. At the lower front edge of the lateral lobes is a 
small triangular sclerite, the pronotal episternum; its companion 
epimeron is lacking. The prosternum is a curiously sculptured 
plate with three deep pits, extending between the bases of the 
front legs. In the neck-membrane, on each side just above and 
in front of the episternum is a pair of very small, linear jugular 
