The humble earthworm should be applauded for its contribution to soil fertility and drainage, says David Profumo.
After centuries as a byword for the lowly, insinuating and contemptible, the common earthworm is now esteemed by ecologists. Darwin pioneered this rehabilitation, concluding ‘it is doubtful whether any other animal has played so important a part in the history of the world’.
There exist more than 1,800 species of terrestrial worm, including an Oregon giant that smells of lilies and an Australian variety that can be heard gurgling underground. Our archetypal specimen is probably the lobworm, Lumbricus terrestris, which belongs to a large group of annulated worms with bristles (setae) on each segment; its taupe head, pinkish, spoon-shaped tail and saddle-like clitellum make it a familiar presence on moist lawns after dusk, whereon it slithers in search of love.
The earthworm has no spine, eyes, teeth or lungs, although it does sport several paired hearts and has sub-muscular chambers filled with coelomic fluid that act as a hydrostatic skeleton. Despite being light-sensitive, it’s practically defenceless (everyone knows what the early bird catches).
The soft, cylindrical body is a powerful, mobile digestive tube with a gut running straight from mouth to anus. In their search for nutritious protein, worms ingest earth and vegetable detritus, which is injected with calcium from unique glands in the oesophagus, ground with mineral particles in the gizzard, then excreted in surface ‘casts’ as humus which enriches the topsoil layer.
Vermian urine also contributes ammonia in minute individual amounts, but the total is considerable: census studies show that, in certain pastures, the worm population runs into several million per acre and can outweigh the livestock grazing overhead. As the cult video-game character Earthworm Jim likes to exclaim: ‘Eat dirt!’
You don’t have to be an oligochaetologist to discern something quietly heroic about the humble worm grinding its slow way through the chthonic underworld. It makes you think differently about the ground beneath your feet. The paramount role of earthworms in maintaining soil fertility and assisting drainage was presciently noted by Gilbert White back in 1770, but it was Darwin who published the first proper monograph (in 1881, just before his death) based on 40 years of fascination.
Worms are quite difficult to study they don’t react well to laboratory conditions and their natural habitat requires laborious excavation and isn’t exactly transparent but Darwin conducted methodical experiments that included spreading the ground with chalk and cinders, blowing whistles and testing the invertebrates’ intelligence with paper triangles coated in fat. He firmly believed they were capable of making choices. It’s been suggested the great naturalist’s near obsession was fuelled by his own chronic digestive problems, which were treated with arsenic and electricity.
Despite its general benefits to soil and geology, the earthworm is not universally welcome. Curators of fine turf resent the surface smears and disfigurements wrought by castings and there’s a vigorous history of vermicidal concoctions ranging from mowrah meal to potassium permanganate.
His Wormship is a prolific breeder ‘much addicted to venery’, in White’s careful phrase but is a hermaphrodite. Each can function as both male and female, but requires cross-fertilisation (Nature’s great process of give and take). On mild, dewy nights, two specimens will overlap ventrally head to tail and copulate for some hours lobworms are known as night crawlers in North America. If you want to glean them for instance, as angling baits you must be dexterous, as their tail-tips are never entirely out of their burrows and they retract swiftly (if broken, their bodies don’t always regenerate).
Seminal fluids are exchanged and the partners finally withdraw, leaving a sealed, lemon-shaped cocoon of mucus within which the eggs are fertilised and from which the transparent wormling will emerge directly there is no larval stage. With the popularity of vermicomposting, commercial farming has become widespread.
Piscatorial literature seethes with advice about procuring various worms along with hints about scouring them in sphagnum moss and feeding them on milk. Some species respond well to vibrations and I remember my first sight of lobworms wriggling to the surface as a stretch of Sutherland sward was mildly electrified to harvest the next day’s salmon bait. The worm on a hook is a widespread emblem of temptation and deceit.
In mythology, a ‘worm’ originally embraced every creeping thing from dragons to snakes Cleopatra’s asp was ‘the pretty worme of Nylus’ but came to be associated with mortality as worms were commonly supposed to consume corpses: Hamlet ingeniously demonstrates how a king’s carcass, via worm and fish, can fetch up inside a beggar. Inevitably, lewdness and phallic undertones also abound from Marvell and Shakespeare to that limerick involving ‘The old Bishop of Birmingham’.
The Maoris uniquely relish worms to eat. As schoolboys, we dubbed our tinned spaghetti ‘worms in blood’, but I cannot reprint what we called the sausages. Even Earthworm Jim wouldn’t have countenanced them.