The pterostigma (plural: pterostigmata) is a cell in the outer wing of insects which is often thickened or coloured and so stands out from other cells. It is particularly noticeable in dragonflies, but present also in other insect groups, such as snakeflies, hymenopterans and megalopterans. Some female damselflies in the family Calopterygidae possess a feature known as a pseudopterostigma. This is similar in location on the wing to a true pterostigma but is crossed by veins and is only defined by its paler colour compared to surrounding areas of the wing.