Visitors to Down House are being reminded of Charles Darwin's profound interest in earthworms, the subject of his final book, often shortened to 'Earthworms'. Darwin dedicated decades to studying these creatures, investigating their intelligence, sensitivity to atmospheric changes, and senses of taste, smell, and hearing.
His research included experiments such as his son Frank attempting to stimulate worms with a bassoon. Darwin also utilised a 'wormstone', a wood-and-copper device, to measure their soil displacement, concluding they move about 2mm of soil annually. He stated that few animals have played such an important part in world history.
Contemporary estimates support Darwin's findings, suggesting that earthworms collectively turn over an amount of soil equivalent to the entire Earth's surface to a depth of one inch every 10 years. They are recognised for their role in aerating, mixing, grinding organic matter, and converting clumps into fertile humus.