Darwin’s orchid tells co-evolutionary tale
Angraecum sesquidapale
Family: Orchidaceae
Conservation Status: Of Least Concern
Because it reliably produces large, white flowers around the winter solstice, it’s no wonder that this native Madagascar epiphyte is known in the West as “the Christmas orchid” or the “Star of Bethlehem orchid.” But the origin of its other common name – Darwin’s orchid – is a longer story.
A key premise of the story: This orchid’s flower features a 10- to 17-inch-long tubular spur that protrudes from the back of the bloom. Nectar fills the bottom 3 to 10 inches of the spur. A potent spicy fragrance at night also helps attract pollinators. Three years after the publication of On the Origin of Species secured Charles Darwin’s reputation as an evolutionary biologist, he predicted that Angraecum sesquipedale could only be pollinated by a “huge moth with a wonderfully long proboscis [in essence, a straw-like tongue]” in his 1862 book The Various Contrivances by Which Orchids are Fertilised by Insects.
The scientific community was skeptical, as the only moths known to inhabit Madagascar were much smaller. But 21 years after Darwin’s death, scientists discovered in Madagascar Xanthopan morgani praedicta — a moth with a 5-to 6-inch wingspan and a 10- to 12-inch proboscis, proving Darwin’s prediction correct.