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#34: Insect Wings

Dragonfly wings

Dipteran (fly) wing

Monarch butterfly wing

Lacewing wings

Litinsects #34: Insect Wings

Let’s talk wings. The ability to fly has existed in only 4 groups of animals: birds 🦅 , bats 🦇 , pterosaurs 🦕, and of course insects 🐞. The first three groups, all vertebrates, each evolved flight independently (in other words, they have no winged ancestor in common) and the wings replace a pair of limbs. Insect wings on the other hand, which first showed up around 400 million years ago, are not derived from legs but are completely separate structures.

The big debate about the evolution of insect wings is whether they developed from pre-existing structures (like gills or extensions of the thorax) or were entirely new structures. There is very little fossil evidence documenting this evolutionary transition so no one has yet definitively answered this question...

  • Insect wings attach to the second and third thoracic segments. At rest they may be held vertically over the back, horizontally out to the sides, tucked over the body, or folded/tucked into place
  • Wings are extensions of the exoskeleton. Hardened veins strengthen the wings and, when intersecting, form “cells” in the membrane. Venation patters are used in identification in many orders of insects
  • There are two different flight mechanisms: direct and indirect flight. Insects with direct flight (mayflies and dragonflies/damselflies) have flight muscles that attach directly to the base of the wings. All other insect groups have indirect flight muscles, which attach to and move the thorax, thereby indirectly moving the wings.
  • Some more primitive insect groups are wingless, such as silverfish and firebrats, but some groups lost their wings secondarily, such as fleas and lice. There may be individual wingless species within winged groups, for example there are species of wingless crickets, beetles, flies, moths, and wasps. Sometimes wings are present only in one sex or social caste, such as in ants and termites and, finally, sometimes wings only arise at specific points in the life cycle, as is the case with aphids
Wings are a fundamental part of insect identification and are one of the main reasons behind the evolutionary success of insects!
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