MEMBRA CIDjE. 
15 
stress on the importance of these veins for classification in the families of insects. 
Others like JBrauer, consider the alary organs to be of secondary importance. 
In this monograph I have employed the alary characters more as a help in 
diagnosis, than made any attempt to found generic distinctions upon them. 
In some families of Homoptera the comparative simplicity of wing frame-work 
is of great value, and it can be relied on, as in Aphis and Coccus. In Cicada, and 
also in Fulgora, Jassus and Membracis, the neuration, taken alone, will be found 
insufficient for sharp separation into genera. 
The Radial Nervures .—The membranous part of the alary system is divided into two 
portions, separated by a suture which mayor may not be strongly marked. The upper part 
or corium is outwardly bounded by the costal nervure, which with the cubitus below 
forms the chief frame-work on which the wing is built. Insensibly the costa unites 
with the apical nervure, bordered by the delicate membranous fold forming the 
limbus, in many, but not in all species. 
For convenience of nomenclature I count four chief radial nervures, which may 
proceed straight to the apex of the tegmen. These may be forked, to inclose additional 
areas or cellules of the tegmen. 
The first radial is the costal. Those following are named the second or cubital, the 
third and fourth raaials. These are succeeded by the sutural fold. 
One radial may be connected with another by short transverse nervures, but 
these are not considered as furcations, for they do not directly run to the margin. 
The lower margin forms the claval suture or bend, which enables the insect to 
fold up this part of the tegmen in small compass under the pronotum. It is not 
always easy to trace this sutural fold in the expanded wing, but it is often shown by 
a kind of notch in the apical membranes. 
A radial may be twice furcated, which of course will increase the number of the 
alar areas enclosed. 
The Transverse Nervures .—These are short connections between the longitudinal 
ribs of the wings. Their variable number, according to the genus or even the species 
of the insect, renders a satisfactory nomenclature difficult. These short nervures 
moreover are not always constant in a series, and sometimes they abnormally appear 
double. On this account, and the tendency shown in some genera of Membracidae 
to develop these transverse nervures in curves, rather than in straight lines, less 
reliance can be given to the wing-neuration for generic diagnosis than is available to 
most other insects. 
Examples of such difficulties may be instanced in Ceresa, Cyphonia, and Bolbonota. 
It may here be noted that in the Membracidse the wings, when folded and at 
rest, are usually carried pent-wise as in Aphides. Thus the costa is seen below the 
