Retinaculum (moth)
Encyclopedia
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". All, but the most basal forms, exhibit this wing-coupling..
The mechanisms are of three different types - jugal, frenulo-retinacular and amplexiform.
) and in the Bombycoidea
(except the Sphingidae
), 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.
The mechanisms are of three different types - jugal, frenulo-retinacular and amplexiform.
Jugal wing-coupling
The more primitive groups 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 have a frenulum on the hindwing that hooks under a retinaculum on the forewing. The retinaculum is a loop 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 (except the male of one species of hesperiidSkipper (butterfly)
A skipper or skipper butterfly is a butterfly of the family Hesperiidae. They are named after their quick, darting flight habits. There are more than 3500 recognized species of skippers and they occur worldwide, but with the greatest diversity in the Neotropical regions of Central and South...
) and in the Bombycoidea
Bombycoidea
Bombycoidea is a superfamily of moths. It contains the silk moths, emperor moths, sphinx moths and relatives. The Lasiocampoidea are close relatives and sometimes merged in the present group. Their larvae exhibit horns.-Sources:...
(except the Sphingidae
Sphingidae
Sphingidae is a family of moths , commonly known as hawk moths, sphinx moths and hornworms, that includes about 1,200 species . It is best represented in the tropics but there are species in every region . They are moderate to large in size and are distinguished among moths for their rapid,...
), 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.