Wing venation is a defining feature of genus.
Some specifics of wing venation can be critical in differentiating between certain congeners [species within the same genus]. For example, one classic case within Europe lies in separating Keeled Skimmers (Orthetrum coerulescens) and Southern Skimmers (Orthetrum brunneum) where the so-called Rspl [Radial supplemental vein] comes into play.
Here is a diagram of dragonfly wings with several occasionally mentioned features indicated.
