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Trait matching between the Madagascan orchid Angraecum sesquipedale, with a nectar spur of 33 cm, and a hawkmoth with a tongue almost as long has fascinated biologists since Darwin, who saw only flowers but correctly predicted the moth pollinator. This moth, Xanthopan morgani praedicta, was described from museum specimens in 1903 and documented as the pollinator in photographs and film in 1992 and 2004. However, Madagascar harbours c. 30 species of long-spurred orchids and seven species of long-tongued hawkmoths, and mutualisms between moths and 'Angraecum and other deep tubular flowers' (Darwin, 1862: p. 202) probably involve a network of interacting species. We infer the evolutionary time over which Madagascan sphingids and Angraecum have interacted, based on an orchid phylogeny that includes 62 of 144 Angraecum species on Madagascar and a moth phylogeny with all nine Madagascan Sphinginae. Clock models using either rate- or fossil-based calibrations imply that the Madagascan subspecies X. morgani praedicta and the African morgani diverged 7.4 +/- 2.8 Mya, which overlaps the divergence of An. sesquipedale from its sister, Angraecum sororium, namely 7.5 +/- 5.2 Mya;since both have extremely long spurs, long spurs probably existed before that. The phylogenies moreover show that several long-tongued moths and long-spurred orchids probably coevolved on Madagascar since the mid-Miocene, although field data on the moths' levels of polyphagy and pollen transport are lacking.

In this review we provide a detailed description of Darwin's prediction of the coevolution of a long‐spurred orchid, Angraecum sesquipedale, and a long‐tongued moth, his correspondence on the subject, the history of the moth and the subsequent literature. On seeing the long spur of A. sesquipedale, Darwin predicted that its pollinator would be a moth with a long proboscis. For more than a century following Darwin's prediction this was assumed to be the case. The pollinator was taken to be Xanthopan morganii praedicta, despite the fact that it had not been observed to visit A. sesquipedale flowers. Direct observations, infra‐red cinematography and photographs published between 1993 and 1997 and a video made in 2004, all of which show X. morganii praedicta visiting A. sesquipedale flowers and removing pollinia, proved that Darwin's prediction was accurate. Recent research suggests that selection pressure exerted by predators on the pollinators, resulted in the evolution of extreme tongue lengths and a special hovering flight. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 403–432.

It started on a quiet day in January 1862 with the arrival of a parcel addressed to Charles Darwin from Robert Bateman. The package contained several orchid specimens needed by Darwin for his research on insect pollination of orchids, including one that took Darwin by surprise. It was the “astounding” Angraecum sesquipedale Thouars, a large orchid with a nectary one foot long! Darwin thought, “what insect could suck it?” (Burkhardt & Smith 1985). And so began a forty-year story that illustrated the power of evolution by natural selection, created a controversy regarding creation, and predicted the existence of a “gigantic moth.”