pterostigma

A pterostigma is a thickened, often colored, cell or patch found near the tip of the wings of insects, particularly in dragonflies and damselflies, but also present in some other insect orders like Hymenoptera. It is a diagnostic feature used in insect identification and taxonomy. The pterostigma is typically rhombus-shaped and covers a portion of both the costa and subcosta veins.

The exact function of the pterostigma has been a subject of scientific inquiry. Current research suggests it plays a crucial role in flight mechanics. By adding mass to the wingtip, the pterostigma can alter the wing's vibrational frequency, potentially preventing flutter or snapping during flight. This stabilization is thought to be particularly important for larger, fast-flying insects like dragonflies. Studies have shown that removing the pterostigma can significantly impair flight efficiency and stability.

The coloration of the pterostigma can vary greatly between species and even within different sexes or age groups of the same species. It can be black, red, brown, yellow, or even transparent. This variation can be a useful characteristic for distinguishing between closely related species. The size and shape of the pterostigma can also differ, providing further taxonomic clues.