mum state of development, they are five in number. The longitudinal one placed along the anterior border of the wing, is usually called the costal nervure: it was named by Jurine, who first gave a nomenclature to these parts, the radius, from a notion that it was analogous to the bone so named in vertebrate animals. For the most part this is the strongest nervure in the wing, as it forms the anterior edge when that organ is extended, and has, therefore, to cut through the air during flight. The nervure next to this, and running parallel with it, is the sub-costal nervure,—the cubitus of Jurine. Both these terminate in an opaque expansion on the anterior border of the wing not far from the middle, which is called the stigma, a term which has been appropriated to a totally different part of structure, but is now in too general use in its twofold sense to be disturbed. The sub-costal gives off, a little before its origin, a third nervure, which runs almost in a direct line towards the centre of the wing, and, at a longer or shorter distance from its commencement, describes numerous zigzag lines; this it has been proposed to call the medial nervure. Beyond this a pretty wide area usually intervenes, which is bounded posteriorly by a nervure running somewhat obliquely towards the centre of the hinder border, which has received the name of sub-medial. The last is more slender than the rest, and has been very appropriately called the anal nervure.
The nervures just described are always more or less united by transverse and recurrent nervures,
