24 
perpendicular above the abdomen, with back to back, in the form of 
a very steep roof, when they are said to be erect. 
The method of folding these organs is unusual. Instead of simply 
raising •them upward so as to bring them back to back, they are drawn 
backward from the expanded condition, keeping the anterior margin be¬ 
low, and elevating the posterior, so that when they come together 
the under sides stand face to face and the posterior margins upwards. 
In others they are placed flat upon the abdomen, slightly overlapping 
at the tips; this position is termed horizontal. 
The venation or number and position of the veins or nerves affords 
most excellent characters, and in order to abbreviate and render more 
certain, descriptions, the following nomenclature of the veins and 
intervening spaces or cells has been agreed upon. 
The front margin is the costa or costal vein , Fig. A. c; the strong 
median vein running from the base (part next the body) outward 
near the front margin, is the sub-costal or sub-marginal vein, sometimes 
termed the cubitus and mid-rib; the hind edge, the posterior margin. 
The oblique vein nearest the base, crossing from the sub costal vein to 
the posterior margin, is the first oblique or first discoidal vein ; the 
next transverse vein is the second oblique or discoidal vein ; the next 
is the third oblique or discoidal vein , but by some it is termed the 
cubital vein; these three veins are sometimes spoken of simply as the 
first, second and third veins. The third of these veins sometimes - 
forks near the middle, sending off a branch towards the apex of the 
wings, this is the first fork or first fur cal vein and continues outward to 
the apex : in many species it likewise forks near the middle, sending 
off a branch to the posterior margin between the extension of the 
first fork and third vein, this is the second fork or second f ureal vein. 
The sub-costal vein, toward the tip of the wing, expands anteriorly, 
connecting with the costa, and forms a somewhat elongate and narrow, 
slightly thickened spot, this is the stigma ; from the posterior side of 
this, near its extremity, starts a slenderer vein which makes a curve 
and extends outward to the apex of the wings, this is the stigmatic 
or fourth vein. 
The cells, or spaces between the veins, generally take their names 
from the neighboring veins, thus: that between the front margin and 
sub-costal vein is the costal cell ; that between the first oblique vein 
and the base, is the basal cell; between the first and second, the 
first discoidal cell; between the second and third, the second discoidal; 
between the third vein and second fork, the first cubital; between the 
first and second forks, the second cubital; between the first fork and 
stigmatic vein, the infra marginal; that between the fourth vein and 
margin, the marginal cell. 
The hind wings have the similar veins and cells named in the same 
manner. 
In the front wings, sometimes the third discoidal vein has but one 
fork, sometimes it is without any, when it is said to be simple; and 
in a few species even one of the branch or discoidal veins is wanting. 
The hind wings usually present two branch or discoidal veins, but 
sometimes there is only one, and sometimes none. 
