Diagram of insect wing venation. Redrawn with modifications from Chapman (fig. 9) The insects: structure and function,
, Cambridge, p.788, (1998)
[1].
The veins are named according to system of Comstock and Needham The wings of insects,
American Naturalist
, Volume 32, p.43-903, (1898)
[2] modified by Wootton Function, homology and terminology in insect wings,
Systematic Entomology
, Volume 4, Number 1, p.81-93, (1979)
[3].
On the right side of the diagram there is a section across the wing. The section was made along the line marked with arrows. It shows, in exaggerated way, corrugation of the wing.

C - costa
Sc - subcosta
R - radius
Rs - radial sector
MA - anterior media
MP - posterior media
CuA - anterior cubitus
CuP - posterior cubitus
1A, 2A, 3A - anals
h - humeral cross-vein
r - radial cross-vein
r-m - radio-medial cross-vein

The wing surface is not flat but corrugated, like a Japanese fan, with alternating ridges and depressions. On the ridges there are convex veins (C, R1, MA, CuA, 1A) and in the depressions there are concave veins (Sc, Rs, MP, CuP). The convex and concave veins are often marked "+" and "-", respectively (e.g. C+, Sc-).