59 
but are best developed in the Orthoptera, Dermaptera, Plecoptera, and 
other primitive insects. 
Tergites. 
As pointed out by Verhoeff, 1903, and Snodgrass, 1909a, the 
notum (or tergum) of many winged insects, consists of two plates — a 
large anterior one, the scutoscutellum (fig. 1, ssl), and a smaller 
transverse posterior one, the postscutellum (psl). Snodgrass terms 
the anterior plate, the notum; but, since the term notum always includes 
the whole notum, or tergum, it is preferable to use the designation 
scutoscutellum for the plate in question, which is largely composed of 
the scutum and scutellum. The posterior plate has always been termed 
the postscutellum, and there is no advantage in changing its name. 
The anterior plate (ssl) is sometimes connected with the pleural 
region by a pre-alar bridge pra (prealare), as in certain Plecoptera, but 
this is usually wanting. The anterior plate bears the wing along its 
lateral margin, and its posterior margin is continued in the posterior 
margin of the wing. The posterior plate ps! lies behind the wing, and 
is sometimes connected laterally with the Ben region by a post-alar 
bridge (pit). 
The anterior plate (Fig. 1, ss!) may be subdivided by the formation 
of infoldings of the body wall (with their external sutures) into the 
following sclerites. 1) A transverse, narrow, anterior, marginal region 
prt (pretergite) which bears the anterior phragma. It is present in 
such insects as Corydalis and Periplaneta, but is often wanting, and is 
always unimportant. 2) A larger, usually triangular median region psc 
praescutum), well developed in most Hymenoptera, Neuroptera, 
Corrodentia, ete. It is sometimes narrow, and transverse, instead of 
triangular (e. g. in Periplaneta). 3) A large central region sc, the 
scutum, which sometimes is united with the praescutum (psc). In cer- 
tain Hymenoptera, the fused scutum and praescutum become secon- 
darily marked off by the formation of new sutures (the so called parapsidal 
furrows of Macleay, 1830) into a median region not strictly homo- 
logous with the praescutum, and two lateral regions pa, which 
Macleay terms parapsides. A small sclerite sur (supraälare or 
suralare) situated immediately above the wing, is marked off from the 
scutum. It serves as a pivot for the wing, in the movements of flight. 
4) In some Hymenoptera, a transverse region prs, the prescutellum, 
situated immediately in front of the scutellum (s), is marked off from 
the remainder of the scutum, by the formation of a distinct crevice, or 
cleft, dividing the anterior plate (ss!) into two “sub-plates”. Emery, 
1900, terms the sclerite in question, the “proscutellum”; but the latter 
term refers to the scutellum of the prothorax (if such exists). It is there- 
