OF INSECTS. 
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enclosing small cells which derive their names from 
the adjacent nervures. Thus the space or cell, 
situate between the costal and sub-costal nervures, 
is called the costal cell ; that bounded by the sub- 
costal and medial nervures, the medial cell ; and 
so on. 
•On attending to the smaller nervures which usually 
occupy the exterior half of the wing, we will per- 
ceive one taking its origin from the stigma or from 
the extremity of the sub-costal nervure, and running 
towards the apex of the wing. This is named the 
radial, and the space between it and the anterior 
margin, the radial cell. The latter is commonly 
divided into two by a secondary nervure, in which 
case there are said to be two radial cells. The ex- 
terior of these is said to be appendaged, when the 
recurrent nervure springs not from the stigma but 
from the external margin of the wing. 
A second nervure, named the cubital, springing 
from the extremity of the sub-costal nervure, or the 
recurrent branch which unites the latter to the 
medial, is directed like the former to the extremity 
of the wing, which it usually reaches a little below 
the apex. The enclosed space is divided by cross 
nervures into cells, which are named cubital cells. 
Between the nervure so named and the suh- 
medial, a considerable space likewise exists, which 
is also divided by intersecting nervures. The cells 
thus formed Latreille has proposed to call dis- 
coidal. Two cells may be observed in the space 
