Theory of Evolution Predicts the Existence of a Species

Both Darwin and his co-discoverer of natural selection, Wallace, called attention to an amazing orchid from Madagascar, Angraecum sesquipedale (see colour page 4), and both men made the same remarkable prediction, which was later triumphantly vindicated. This orchid has tubular nectaries that reach down more than 11 inches by Darwin's own ruler. That's nearly 30 centimetres. A related species, Angraecum longicalcar, has nectar-bearing spurs that are even longer, up to 40 centimetres (more than 15 inches). Darwin, purely on the strength of A. sesquipedale's existence in Madagascar, predicted in his orchid book of 1862 that there must be 'moths capable of extension to a length of between ten and eleven inches'. Wallace, five years later (it isn't clear whether he had read Darwin's book) mentioned several moths whose probosces were nearly long enough to meet the case.

For the flower, insect pollination represents a huge advance in economy over the wasteful scattergun of wind pollination. Even if a bee visits flowers indiscriminately, lurching promiscuously from buttercup to cornflower, from poppy to celandine, a pollen grain clinging to its hairy abdomen has a much greater chance of hitting the right target - a second flower of the same species - than it would have if scattered on the wind. Slightly better would be a bee with a preference for a particular colour, say blue. Or a bee that, while not having any long-term colour preference, tends to form colour habits, so that it chooses colours in runs. Better still would be an insect that visits flowers of only one species. And there are flowers, like the Madagascar orchid that inspired the Darwin/Wallace prediction, whose nectar is available only to certain insects that specialize in that kind of flower and benefit from their monopoly over it. Those Madagascar moths are the ultimate magic bullets.

The existence of an orchid means there must be a species adapted to reaching its nectar.