1927} Thoracic Sclerites and Wing Bases of the Roach 69 
from the standpoint of phylogeny, and these structures likewise 
serve as landmarks in determining the location of certain veins, 
areas etc., of the wing. The basal fold bp and pocket-like sinus 
bsi are very prominent in the fore wings of roaches, termites, 
the Hemiptera with coriaceous fore wings, etc., and it is very 
probable that these structures were developed in order to fa- 
cilitate the folding back of the fore wings, when these are laid 
along the top of the abdomen in repose (see Bull. Brooklyn Ent. 
Soc., 1927). I shall again refer to these structures in a paper 
dealing with the basal region of the wings of insects in general, 
so that it is not necessary to discuss the matter further at this time. 
As was mentioned above, a postanal, or postclaval ridge (or 
in some cases a rima, or crack-like line) labelled po in Figs. 6, 7, 
8, 9, 10 and 16, demarks the axillary, or alular region, from the 
anal, or claval region of the fore wings. A preanal, or preclaval 
rima cl demarks the anal area of the wing from the median region 
of the wing, and the rima cl may be regarded as a “rima dividens” 
paralleling the “vena dividens” described by Comstock and 
others, in this region of the wing. A median rima, in front of 
the rima labelled cl in Figs. 10 and 16, demarks the median area 
of the wing from the radial area, in some insects, and a costal 
area ca of Fig. 16, is frequently demarked by the subcostal vein 
Sc in roaches, termites etc. 
On the under side of the fore wing of the roach, as shown 
in Fig. 2, there is an important ventral ridge, the subcostal 
crista or plica scr, extending along the subcostal vein, and the 
condition exhibited in this region of the fore wing of the roach 
is of considerable interest from the standpoint of phylogeny, 
since the tegmen (fore wing) of the roach offers a very suitable 
startingpoint for tracing the modifications in this area of the 
elytra of beetles and the fore wings of other insects descended 
from roach-like forebears in the common Protorthopteran-Pro- 
toblattid stem. 
When the fore wing of the roach is laid back in repose, it 
assumes the position shown in Fig. 2; and a protuberance m of 
the epimeron em 2 fits into a cavity in which the sclerite d at the 
base of the subcostal vein (or subcostal ridge scr) is located. 
The subcostal ridge scr lies above, and mesal to, the projecting 
