April 07, 2006

Worm grunting

If you happen to be in Sopchoppy, Florida tomorrow, you might want to stop in at the sixth annual Worm Grunting Festival, which offers a unique combination of science and folklore.

The science starts with Charles Darwin's last work, "The Formation of Vegetable Mould Through the Action of Worms, With Observations on Their Habits", which includes a charming account of his experiments:

Worms do not possess any sense of hearing. They took not the least notice of the shrill notes from a metal whistle, which was repeatedly sounded near them; nor did they of the deepest and loudest tones of a bassoon. They were indifferent to shouts, if care was taken that the breath did not strike them. When placed on a table close to the keys of a piano, which was played as loudly as possible, they remained perfectly quiet. Although they are indifferent to undulations in the air audible by us, they are extremely sensitive to vibrations in any solid object. When the pots containing two worms which had remained quite indifferent to the sound of the piano, were placed on this instrument, and the note C in the bass clef was struck, both instantly retreated into their burrows. After a time they emerged, and when G above the line in the treble clef was struck they again retreated. Under similar circumstances on another night one worm dashed into its burrow on a very high note being struck only once, and the other worm when C in the treble clef was struck. On these occasions the worms were not touching the sides of the pots, which stood in saucers; so that the vibrations, before reaching their bodies, had to pass from the sounding board of the piano, through the saucer, the bottom of the pot and the damp, not very compact earth on which they lay with their tails in their burrows. They often showed their sensitiveness when the pot in which they lived, or the table on which the pot stood, was accidentally and lightly struck; but they appeared less sensitive to such jars than to the vibrations of the piano; and their sensitiveness to jars varied much at different times.

It has often been said that if the ground is beaten or otherwise made to tremble, worms believe that they are pursued by a mole and leave their burrows. From one account that I have received, I have no doubt that this is often the case; but a gentleman informs me that he lately saw eight or ten worms leave their burrows and crawl about the grass on some boggy land on which two men had just trampled while setting a trap; and this occurred in a part of Ireland where there were no moles. I have been assured by a Volunteer that he has often seen many large earth-worms crawling quickly about the grass, a few minutes after his company had fired a volley with blank cartridges. The Peewit (Tringa vanellus, Linn.) seems to know instinctively that worms will emerge if the ground is made to tremble; for Bishop Stanley states (as I hear from Mr. Moorhouse) that a young peewit kept in confinement used to stand on one leg and beat the turf with the other leg until the worms crawled out of their burrows, when they were instantly devoured. Nevertheless, worms do not invariably leave their burrows when the ground is made to tremble, as I know by having beaten it with a spade, but perhaps it was beaten too violently.

According to a 4/7/2006 story by Kevin Begos in the Tampa Tribune, the folklore involves "[t]he backwoods craft of rubbing a metal bar against a wood stake [which] produces vibrations that drive earthworms out of the ground. Sopchoppy might be the only place where people make their living harvesting wild earthworms this way, then selling them to bait shops as far away as the Midwest."

"I do have two children, and they can both grunt worms. Absolutely. It's something that I want to hand down to them," Debbie Chane said. "It was something that my daddy handed down to me and his daddy handed down to him. I want them to know a little bit of their heritage and their tradition."

Darwin would have been enthralled. But what I want to know is, what is the scientific explanation for the folkloric secret of worm-calling that eluded Darwin? Was it really a matter of amplitude, as he speculated? Or did his spade produce the wrong vibration spectrum, whacks as opposed to grunts?

Posted by Mark Liberman at April 7, 2006 09:46 AM