24 THE AMERICAN NATURALIST. [Vor. XXXVI. 
pleurites of the prothorax are distinct from the sternum on 
the one hand and from the tergum on the other; more often, 
however, the tergite of the prothorax is not separated from 
the pleurites. This is also the case in the segments of the 
head: sometimes the tergite is distinct from the pleurites; 
|. but more often the tergite is merely a 
continuation of the pleurites over the 
dorsal side of the segment. In such 
cases the combined lateral and dorsal 
. parts are designated as the pleurites ; for 
we find that they bear the most charac- 
teristic feature of the pleurites, the 
lateral apodemes, to be described later. 
owes Equally important for the purposes 
Fic. r2.— Ventral aspect of the of this study is the fact that each 
metathorax of a nymph of K n 
PATRONS, thoracic segment is composed of two 
subsegments. It is not necessary for 
us to decide in this place whether or not this indicates a fusion 
between two primary metameres, as has been suggested by 
_ various writers!; the essential fact which must be taken into 
account is the transverse division of each segment. The line 
separating the subsegments. passes, on the pleural aspect, 
between the episternum and the epimeron ; and, on the tergal 
aspect, between the scutum and the scutellum. On the sternal 
aspect, in most insects, the 
division is not easily recog- 
nized; but in certain Ple- 
coptera and Orthoptera it 
can be readily seen. 
Fig. 12 represents the 
sternite of the metathorax 
of a nymph of Pteronarcys, pia. r3.—Ventral 








2 aspect of the metathorax of Steno. 
and Fig. 13 the same part pelmatus. The position of the furca within the 
body i ted by a dotted li 
of Stenopelmatus. In each is represented by a dotted line. 
case it can be seen that the sternite is composed of two 
distinct sclerites, — one lying between the episterna and one 
: 1 The reasons for believing that each soient e ipon dC two, primy 
netame cuir apu ee 

Lowe 




