Remember the story of Tiktaalik, the missing piece in the evolution that connected fishes and four-legged animals? Here is another equally exciting example. And how Darwin predicted the existence of a species after seeing a flower!
In 1862, Charles Darwin received a box of orchids from a well-known grower of his time. Among them was Angraecum Sesquipedale. Check the link to see how it appears. Look at the long spur or nectary, the nectar-secreting organ in the flower. Seeing the extraordinarily long nectary, Darwin wondered about the existence of moths with long tongues. As nectar-liking moths are crucial agents for pollination, such an orchid would not have evolved without the help of a moth with fitting organs.
In 1907, years after Darwin’s death in 1892, the culprit was found – Xanthopan Morganii Praedicta, from Madagascar!
To conclude this story, in the 1990s, biologists made direct observations of the meeting of the two. See the cover page of the Botanica Acta of 1997.
Reference
Arditti et al., ‘Good Heavens what insect can suck it’– Charles Darwin, Angraecum sesquipedale and Xanthopan morganii praedicta, Botanical Journal of the Linnean Society, 2012, 169, 403–432.