OF INSECTS. 301 



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 sub- 

 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 



