Page:Jardine Naturalist's library Entomology.djvu/307

Rh 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 perceive 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 exterior 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 discoidal. Two cells may be observed in the space