1925] External Anatomy of Head and Abdomen of the Roach 207 
million of years despite the vicissitudes of time and changing 
environment! 
The typical tergites and sternites are composed of two prin- 
cipal areas. In the tergite the anterior area (demarked by a 
transtergal suture or ridge) is the antetergite at (Fig. 14) and the 
posterior region is the tergite proper or eutergite etg. Similarly, 
in the sternal plate there is an antesternite as and a sternite 
proper or eusternite ens seperated by a transternal suture or 
ridge. The antetergite and antesternite are apparently demarked 
by the friction of the overlapping edges of the telescoping seg- 
ments, or at any rate, the antetergite and antesternite are usual- 
ly over-lapped by the posterior portions of the preceding segments 
and are usually less deeply pigmented than the rest of the tergal 
and sternal sclerites. The telescoping of the segments of the 
abdomen allows for distention with eggs, etc., and in its normal 
state the abdomen of the female is more flattened than is the 
case with the egg-distended abdomen shown in Fig. 14; and the 
anterior portions of the sternal and terga are usually hidden in 
non-distend individuals. 
Following the generally accepted usage of systematists, I 
have restricted the use of the terms tergite, pleurite and sternite 
to the dorsal, lateral and sternal plates of the abdomen alone, 
and I would use the designations notum, pleurum and sternum 
for the parts of the thoracic segments. The segments of the ab- 
domen may be referred to as the uromeres, for the sake of brev- 
ity, and counting from the base of the abdomen, I would refer to 
them as uromere 1, uromere 2, etc., instead of using the longer 
designation “first abdominal segment, second abdominal seg- 
ment,” etc. The terminal abdominal segments and their various 
structures are referred to as the terminalia (Crampton, 1918) 
but Freeborn, 1924, includes in the designation “terminalia” 
the genital structures as well in higher insects, and the latter 
usage is preferable in the higher forms where the genitalia and 
terminal structures are compactly grouped by the shortening 
and telescoping of the terminal segments of the abdomen. When 
there is a reduction in the number of the abdominal segments, 
it is usually the terminal ones which fuse or unite, as is indicated 
by the fact that the spiracles remain distinct (for the most part) 
