I believe that there are times when the greatest fulfillment comes from letting tangents and coincidence guide one's attention. Well, coincident with the attention given to Darwin's two-hundredth birthday, my wife's specimen of Darwin's Orchid decided to bloom, and so it cried out for a snapshot today.
This genus is native to Madagascar. It has an elongated nectary - up to a foot long - extending from the back of the flower. Nectar is contained in the tip of the nectary. Darwin reasoned that there must be some species of moth with a proboscis long enough to reach the length of the nectary, but this hypothesis was ridiculed by others in his day.
The idea that such a long-tongued moth would have evolved is no longer considered ridiculous. Such a moth was indeed discovered years later.
This fascinating video from a Nature episode shows the moth in action with Darwin's Orchid:
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