Wing coupling

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Wing coupling

Some four-winged insect orders, such as the Lepidoptera, have developed a wide variety of morphological wing coupling mechanisms in the imago which render these taxa as "functionally dipterous" (effectively two-winged) for efficient insect flight.[1] All but the most basal forms exhibit this wing coupling.[2]:4266

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Oiketicus spp. (family Psychidae). The frenulum can be seen at the top of the rear wing, which hooks onto the retinaculum, seen here as a small brush on the front wing, so that the wings travel together during flight. Magnification: 10x

The mechanisms are of three different types - jugal, frenulo-retinacular and amplexiform.[3]

Jugal wing coupling

The more primitive groups of moth have an enlarged lobe-like area near the basal posterior margin, i.e. at the base of the forewing, called jugum, that folds under the hindwing in flight.[2][4]:631–664

Frenulo-retinacular wing coupling

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Examples of frenulo-retinacular wing coupling in male and female moths

Other groups of moth have a frenulum on the hindwing that hooks under a retinaculum on the forewing.[4] The retinaculum is a hook or tuft on the underside of the forewing of some moths. Along with the frenulum, a spine at the base of the forward or costal edge of the hindwing, it forms a coupling mechanism for the front and rear wings of the moth.

Amplexiform wing coupling

In the butterflies[a] and in the Bombycoidea[b], there is no arrangement of frenulum and retinaculum to couple the wings. Instead, an enlarged humeral area of the hindwing is broadly overlapped by the forewing. Despite the absence of a specific mechanical connection, the wings overlap and operate in phase. The power stroke of the forewing pushes down the hindwing in unison. This type of coupling is a variation of frenate type but where the frenulum and retinaculum are completely lost.[1][5]

Notes

  1. The male of one species of hesperiid (skipper) butterfly does have wing couplings.
  2. The Sphingidae (hawk moths) however do have wing couplings.

References

Sources

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