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What Insect Can Suck It?

Scientists love their jargon so much, they make new jargon all the time. Scientists love their jargon so much that single words are not enough: in fact, there are stories about science that have basically become jargon. Recognizing the story is a secret handshake, a knowing nod to those others in the circle. The story of Darwin’s moth is just such a story.

Charles Darwin, pictured with epic beard and eyes full of evolutionary theory. Photo is USA public domain, and retrieved from wikicommons.

Nowadays, Charles Darwin is remembered more for his theory of evolution and epic beard than he is for all the work he did as a naturalist. It was his tireless observations and cataloging of living things all over the world that led him to develop his theory. The Origin of Species, Darwin’s famous book on the theory of evolution was published in 1859, and by the early 1860s, Darwin was full throttle into another one of his projects: the cataloging of the way that plants get pollinated by insects, the results of which were published in The Fertilisation of Orchids.

Orchids are kind of a perfect subject for pollination experiments and observations. There are up to 26,000 different species of orchids, and many of them have very specific pollinators. Unlike many species, which can be pollinated by a number of different insects, most orchid species have very distinct and specialized flowers that have evolved to attract specific insects. Orchids are pollination super-stars, and Darwin recognized their importance.

Angraecum sesquipedale illustration from Fitch, Warner and Williams. USA public domain. You can see it's nectar spurs here: they're the very long bits extending from the flower.

Orchids are found across the world, and even though Darwin did his share of exploration on the Beagle, he relied on friends and colleagues to pass along to him orchid samples that they collected. James Bateman was just such a colleague. In early 1862, Bateman sent Darwin several flowers from the orchid Angraecum sesquipedale. The flower had been discovered and then described decades earlier, but no one had any idea how it was pollinated.

That’s where Darwin steps in. Sort of. Upon examining the flower, he notices that the nectar spur is especially long ““ over a foot in length. Darwin also noticed that the only way to collect the pollen from the orchid, a task necessary for successful pollination, was to place a thin cylinder down the entire length of the spur. In order to pollinate the plant, some insect had to be able to reach all the way down that pollen spur. Darwin hypothesized that somewhere, there was an insect with a proboscis (a straw-like tongue that some insects have) over a foot in length. Clearly, this opened up the door for many your-mom/dick jokes and a lot of general derision. It didn’t help when he himself wrote in a letter “Good Heavens what insect can suck it” in reference to this orchid.

Xanthopan morgani from the Natural History Museum of London, photo by wiki-user Esculapio. This insect can suck it - check out that proboscis!

Over two decades after Charles Darwin shuffled off this mortal coil, just such an insect was found: Xanthopan morgani, a hawk moth with a prodigious proboscis, was discovered in Madagascar in 1903. Just as Darwin predicted, this moth with the foot-long proboscis was the pollinator for the orchid with the foot-long nectar spur. I bet he was saying “I told you so” from beyond the grave. Nowadays, this story is known by biologists everywhere as a primo example of how the theory of evolution can make real predictions about what we can expect to see in the world around us.

4 replies on “What Insect Can Suck It?”

This is so cool!  Thanks for sharing.

Although I have to say when I first read the title, I thought it was some sort of poll and you meant “What insect can proverbially suck it?” I was going to say earwigs. Earwigs can suck it. They freak me out.

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