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Some four-winged insect orders, such as the
Other groups of moth have a frenulum on the hindwing that hooks under a retinaculum on the forewing. The retinaculum is a hook or tuft on the underside of the forewing of some
Some four-winged insect orders, such as the Lepidoptera
Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...
, have developed a wide variety of morphological wing coupling mechanisms in the imago
In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the ''imaginal'' stage ("imaginal" being "imago" in adjective form), the stage in wh ...
which render these taxa as "functionally dipterous" (effectively two-winged) for efficient insect flight
Insects are the only group of invertebrates that have evolved insect wing, wings and flight. Insects first flew in the Carboniferous, some 300 to 350 million years ago, making them the first animals to evolve flight. Wings may have evolved from ...
. All but the most basal forms exhibit this wing coupling.
The mechanisms are of three different types - jugal, frenulo-retinacular and amplexiform. Subsec. "Wing coupling". Pp 56-60.
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.Frenulo-retinacular wing coupling
Other groups of moth have a frenulum on the hindwing that hooks under a retinaculum on the forewing. The retinaculum is a hook or tuft on the underside of the forewing of some moth
Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
s. 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 thebutterflies
Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...
and in the Bombycoidea
Bombycoidea is a superfamily of moths, including the silk moths, giant silk moths, sphinx moths, saturniids, and relatives. The superfamily Lasiocampoidea is a close relative and was historically sometimes merged in this group. After many ...
, 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.
Notes
References
{{reflist, 28emSources
* Pinhey, E (1962). ''Hawk Moths of Central and Southern Africa''. Longmans Southern Africa, Cape Town. Insect anatomy