MORSE: ORTHOI'TKIJA OK NKW KNCLAND. 221 
sclerites, which aid in supporting the head. These show hotter in 
the Dusky Locust (Encoptnlophus. sonlidus), black in a brown 
membrane. The hind margin of the (hsk of the pronotum extends 
backward to form a right angle and is often referred to as the 
hind process of the pronotum. In the membrane connecting the 
prothorax and mesothorax, under the ventral portion of the 
lateral lobes, one on each side, are the prothoracic spiracles, 
openings into the system of air-tubes (tracheae, singular trachea) 
which conduct air to all parts of the body. Directly above the 
fossa from which arises the middle leg is another spiracle, 
guarded by a pair of lips which open in a nearly vertical plane, 
and surrounded by a narrow sclerite termed a peritremc. These 
are the mesothoracic spiracles. 
The mesothorax is rigidly united to the metathorax. Ventrally 
the sterna of these two segments appear as broad transverse 
plates, notched in the mid-line posteriorly by a wade quadrate 
interspace. The mesosternal interspace is occupied by a part of 
the metasternum, the metasternal interspace by a corresponding 
part of the first abdominal segment. Laterally, the four pleural 
plates (mes- and metepisterna and epimera) appear as rather 
narrow, elongate, somewhat oblique sclerites extending from the 
sterna and fossae of the legs dorsally to the notum and attachment 
of the wings. In some species of Melanoplus the metepisternum 
is characteristically marked by an oblique pale stripe. 
The dorsum of these two segments of the thorax is entirely 
covered by the hind process of the pronotum, and the bases of 
the tegmina and wings. When exposed it presents an intricately 
sculptured surface composed mainly of four sclerites, — the 
scutum and scutellum of each of the two segments. 
Appendages of the Thorax: Legs. — Each leg (Fig. 9) is made up 
of a series of segments of which a short, somewhat conical basal 
one, the coxa (plural coxae), is attached to the thorax in such a 
way as to allow movement in every direction. To it a long 
segment, the thigh or femur (plural femora) is articulated by a 
hinge-joint moving vertically. Next comes a long shank (tibia, 
plural tibiae), armed beneath in the front and middle legs, above 
in the hind legs, with two rows of stiff black spines. On the 
front and middle legs these are movably attached,^ on the hind 
legs rigidl}', with the exception of two pairs of longer spurs at the 
