Charles Darwin spent years studying the behaviour of lumbricus terrestris, the common earthworm, in the garden of his home in Kent, and even wrote a book about them. He had a wormstone to show how their earthmoving made objects on the surface sink into the ground - an effect he observed at Stonehenge. His obsessional interest in a slimy lower life form was not misplaced, because the worm’s sole function of digesting vegetable matter and subsoil, and depositing it on the surface in nitrogen-rich casts, is partly responsible for life as we know it.

After the last ice age 10,000 years ago, civilisation flourished around the Nile, Indus and Euphrates rivers, where large populations of earthworms kept the soil in top condition. Cleopatra deemed them sacred and her people were banned from taking these natural fertilisers out of the ground. Worm eggs, possibly carried on the hooves of colonists’ horses, took the earthworm to North America, where they cultivated the previously unworkable soil.

The earthworm’s body is little more than a succession of guts surrounded by muscle which contracts and expands to propel it along. Cold-blooded invertebrate hermaphrodites, worms breathe through their skin and have five pairs of hearts arranged near their anterior, or front end. But it’s a myth that chopping one in half creates two new worms - those lifelike wriggles are, in fact, extended death spasms.

Worms are the staple food of badgers and moles, the bait to land fish and the reward of the early bird. With more than a million in every acre of cultivated land, there are plenty to go round. Found in the form of a computer virus, mimicking its native cousins by burrowing into computer systems, or as an intestinal invader of animals or humans, the worm is less welcome. And, of course, a can of worms is best left unopened - even though the original meaning of this writhing mass of complications is buried in the metaphorical mud.

harvey mcgavin