Diagram of wing venation
for glossary entry
on same. (This is Anisopa
, a member of the wood gnats, Anisopidae
.) Caption based on Comstock (1)
, with some additions and editing:
The principal veins of the wing, those that arise at or near the base of the wing, are termed, beginning with the one lying on the costal margin, the costa
, the subcosta
, the radius
, the media
, the cubitus
, and the anal veins
. The radius, media, and cubitus are usually branched, and there may be several anal veins.
In addition to the principal or longitudinal veins, there may be a greater or less number of cross-veins
--veins extending transversely from one longitudinal vein to another. In the lettering of figures, abbreviations of the names can be used as is done in the figure above (wing of a fly, Anisopus
The divisions of a branched vein are numbered, beginning with the one nearest the costal margin of the wing; and these numbers are indicated by sub-figures. For example, the five branches of the typical radius are designated thus, R1, R2, R3, R4, R5.
When two or more branches of a branched vein coalesce, the compound vein is designated by an expression indicating this coalescence, as R2+3. In this way it is possible to indicate some of the changes that have taken place in the development of the species; and to make use of them in working out the classification of the group to which the species belongs.
The cells of the wing are designated by applying to each the number or the abbreviation of the name of the vein that forms its cephalic (front) margin. In the figure above, the veins are designated by letters at the margin of the figure; the cells by letters within the figure. When a cell is divided by a cross-vein the parts are numbered, as in the case of cell M2 in the figure.