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The pterostigma (plural: pterostigmata) is a group of specialized cells in the outer
The pterostigma (plural: pterostigmata) is a group of specialized cells in the outer wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
s of insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s, which are often thickened or coloured, and thus stand out from other cells. It is particularly noticeable in dragonflies
A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threa ...
, but present also in other insect groups, such as snakeflies, hymenoptera
Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
ns, and megaloptera
Megaloptera is an order of insects. It contains the alderflies, dobsonflies and fishflies, and there are about 300 known species.
The order's name comes from Ancient Greek, from ''mega-'' (μέγα-) "large" + ''pteryx'' (πτέρυξ) "wing ...
ns.
Purpose
The pterostigma, a heavier section of the wing than nearby sections, assists in gliding. Without the pterostigmata, self-exciting vibrations known as flutter would set in on the wing above a certain critical speed, making gliding impossible. Tests show that with the pterostigmata, the critical gliding speed is increased 10–25% on one species of dragonfly.Pseudopterostigma
Some femaledamselflies
Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies, which constitute the other odonatan suborder, Anisoptera, but are smaller and have slimmer bodies. Most species fold the wings along ...
in the family Calopterygidae
The Calopterygidae are a family of damselflies, in the suborder Zygoptera.
They are commonly known as the broad-winged damselflies, demoiselles, or jewelwings. These rather large damselflies have wingspans of 50–80 mm (compared to about 44 ...
possess 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.
References
{{Reflist Insect anatomy it:Glossario entomologico#pterostigma