Sunday, February 21, 2010

Proboscis prediction

I mentioned the Madagascar Star Orchid, aka Star of Bethlehem orchid, comet orchid and Darwin's orchid when we talked about evolution.

Based on the extremely long corolla (about a foot in length) the moths would need to probe to get the nectar Darwin deduced that there must be moths with extremely long tongues in Madagascar even though he never saw them:

"It is, however, surprising that any insect should be able to reach the nectar: our English sphinxes have probosces as long as their bodies: but in Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches!" Darwin, 1862 in On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing.

This photo was the Botany Photo of the day on Feb 12th and they include a link to an interesting paper in the American Entomologist entitled Darwin's Madagascan Hawk Moth Prediction that describes how Darwin's description of the orchid and proposed moth was ridiculed by some as being impossible while others suggested the long nectaries were proof of supernatural creation. Darwin and Wallace went on to explain how evolutionary processes could develop both a long-nectaried orchid species and a co-evolved moth.

Unfortunately Darwin did not live long enough to see the discovery of the moth in 1903. Although the moth was originally named "praedicta" in honor of the fact that Darwin predicted its existence the name was later, unfortunately, changed.

The moth approaches the flower to ascertain by scent whether or not it is the correct orchid species. Then the moth backs up over a foot and unrolls its proboscis, then flies forward, inserting it into the orchid's spur.

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