Pterostigma

Spotted darter with distinct wing marks

The pterostigma or wing mark is a particularly pronounced field in the wing of dragonflies and many other flying insects. It is also found, for example, in aphids , hymenoptera , dust lice , ant maids , netwings and hover flies . The pterostigma is located on the leading edge of the forewing tips (in dragonflies also the rear wing tips) and is usually somewhat enlarged and often dark in color. The existence and development of the pterostigma is used in dragonflies to identify the species and for their systematic classification.

There are various attempts to explain the function:

• The pterostigma is probably still in the dragonflies' field of vision and is used by the animals to navigate between vertical structures during flight without bumping their wings.
• Another conceivable function is that of a vibration stop . The hemolymph in the pterostigma and the condensing wing veins weigh down and at the same time stiffen the wing edges, which prevents the wing from resonating .
• Furthermore, the reinforcement of the most stressed area could prevent damage to the wing.