Xanthopan morgani, or Morgan's Sphinx, is a very large hawk moth from West Africa (Rhodesia, Nyasaland) and Madagascar. It is the sole member of its genus, and little is known of the biology, though the adults have been found to visit orchids (see below), and it is believed that the larvae feed on Uvaria.
The English naturalist Charles Darwin observed a remarkable orchid, Angraecum sesquipedale, while in Madagascar during his five year voyage on the Beagle. Darwin noted the defining characteristic of the species: its extremely long spur. The spur of the flower is 20-35 cm from its tip to the tip of the flower's lip. The name "sesquipedale" is Latin for "one and a half feet," referring to the spur length. From his observations, Darwin surmised, in his 1862 publication "On the various contrivances by which British and foreign orchids are fertilised by insects", that there must be a pollinator moth with a proboscis long enough to reach the nectar at the end of the spur. In its attempt to get the nectar and the end of the spur the moth would get pollen rubbed off on its head. The next orchid it visited would then be pollinated in the same manner. In 1903, such a moth was discovered in Madagascar, and named Xanthopan morganii praedicta. The subspecific epithet "praedicta" was given in honor of the fact that Darwin predicted its existence, though the subspecies was later determined to be invalid (it is identical to the mainland form of the species). The moth approaches the flower to ascertain by scent whether or not it is the correct orchid species. Then the moth backs up over a foot and unrolls its proboscis, then flies forward, inserting it into the orchid's spur.