124 
Psyche 
J une-August 
with that of the radial follows, if it is assumed that the radial 
is a high nervure while its sector is a low nervuref then the an- 
terior median is a high nervure, the posterior a low nervure. 
The sector of the median is missing in the Perlids and con- 
sequently does not figure in Comstock’s scheme. I have 
shown that this nervure is very short and that it rejoins the 
cubital, or rather that it is completely lost in all the Orthoptera 
{sensu latissimo, including the Perlids) ; Tilly ard has also shown 
that the same thing happens to the sector of the median (which 
he calls M^) in the Holometabola.^ 
The cubital nervure has a configuration exactly like that of 
the radial and median; even nearer the base of the wing than 
does the median, it divides into two branches, an upper anterior, 
which I have called anterior cubital, and a lower posterior, the 
the posterior cubital, which is in a way the sector of the cubital . 
Thus radial, median, and cubital show an identical form 
among the primitive insects, consisting of an upper vein followed 
by a lower sector. 
Now we may ask if the same plan does not apply to the other 
nervures. 
The costal is a high nervure, the sub-costal a low nervure, 
although the sub-costal appears not to be a branch of the costal, 
but arises directly behind the costal from the anterior tracheal 
(trunk) of the wing, it seems to me that we must admit that the 
sub-costal is the sector of the costal. 
In the living insects only three anal nervures are found; 
but an examination of the fossils from the coal measures shows 
that there are apparently many more, for they are branched. 
I distinguish a first upper anal, a second lower anal, a third upper 
anal followed frequently by lower branches. I believe that we 
find but two anal nervures, the so-called second anal being the 
sector of the first. 
The wing thus contains six (principal) nervures, three 
forming the anterior group: the costal, the radial, the median; 
and three belonging to the posterior group: the cubital, a first 
anal (lA) which we may call the penultimate, and a second anal 
