In 1862 Charles Darwin examined Angraecum sesquipedale, a Madagascan orchid whose nectar is held at the base of a spur roughly 25 to 30 centimetres long. He concluded that some insect must exist with a proboscis long enough to reach it, since otherwise the flower could not be pollinated. Alfred Russel Wallace later supported the prediction and suggested it would be a hawkmoth related to African species.
A Madagascan hawkmoth matching the description was formally named in 1903 as a subspecies of Xanthopan morganii, and the subspecies epithet praedicta records the prediction. Direct evidence that it actually pollinates the orchid took much longer: filmed observations of the moth feeding at Angraecum sesquipedale in the wild were published in 1992, 130 years after Darwin's inference.
In 2021 a revision elevated the Madagascan population to full species rank as Xanthopan praedicta, on morphological and genetic grounds, and reported that its proboscis averages longer than that of its African relative. Whether the orchid and moth coevolved through a race of escalating lengths, or the moth's proboscis evolved first for other flowers, is still argued.