When studying Angraecum sesquipedale, Charles Darwin theorised that, since the nectar was at the bottom of the spur, a pollinator must exist with a tongue at least as long as the spur. Otherwise the orchid could never be pollinated. At the time, he was not believed. However, long after Darwin's death, the predicted pollinator was discovered, a hawk moth now named Xanthopan morganii praedicta (praedicta meaning predicted). It had an appropriately long proboscis. This was a perfect example of mutual dependence of an orchid and a specific pollinator.

Angraecum sesquipedale has a nectar tube of 25-30 cm (10-12 in.) in length with only the distal end filled with nectar. Charles Darwin postulated that there must be an as yet undiscovered moth with a proboscis cabable of extending to 11 in.(28 cm) that visits this flower. This moth (Xanthopan morgani praedicta) was 'discovered' over 41 years later in 1903 even though its existence had been postulated earlier.

 Top