In many moths the wing coupling is done by a tiny hook going round a tiny spur. In butterflies and some moths the wing coupling is got by wing overlap, rather than hooks.
Sphingid moths have been much studied for their flying ability, especially their ability to move rapidly from side to side while hovering, called "swing-hovering" or "side-slipping". This is thought to have evolved to deal with ambush predators that lie in wait in flowers.
- Dudley, Robert (2002). The biomechanics of insect flight: form, function, evolution. Princeton University Press. p. 476. ISBN 978-0-691-09491-5.
- Kitching, Ian J (2002). "The phylogenetic relationships of Morgan's Sphinx, Xanthopan morganii (Walker), the tribe Acherontiini, and allied long-tongued hawkmoths (Lepidoptera: Sphingidae, Sphinginae)". Zoological Journal of the Linnean Society. 135 (4): 471–527. doi:10.1046/j.1096-3642.2002.00021.x.