Ground force

On a mild, wet, early morning last autumn, I came across two earthworms (Lumbricus terrestris) mating on the lawn. At the vibration of my tread, they split apart and, though I try not to anthropomorphise animals (I could never have gone fox hunting if I had), such behaviour did look shifty, as if I had surprised a teenage couple entwined on the family sofa.

I had never before in my life seen such a coupling, which is remarkable considering how many early mornings I have spent in gardens and how common earthworms are, but it underlines the fact that their lives are mostly spent hidden from sight underground. Their influence on our lives is usually therefore hugely underestimated — except perhaps by farmers and gardeners.

The pioneering research on earthworms was done, as everyone knows, by Charles Darwin, culminating in the publication in 1881 of The Formation of Vegetable Mould, Through the Action of Worms, with Observations on their Habits. Much of what we generally know about worms comes from this: Darwin called them ‘Nature’s plough’ and reckoned that an acre contained 50,000 worms with the capacity to ingest and expel 18 tons of casts a year, aerating the soil with their tunnels and, in the process, transforming it:

Their chief work is to sift the finer from the coarser particles, to mingle the whole with vegetable debris, and to saturate it with their intestinal secretions….

In fact, later researchers have discovered that there are far more than 50,000 earthworms in the average acre, but the point is still a good one. According to Darwin, it is also thanks to earthworms that so many Roman remains lay, and lie, intact, safe and sound under a blanket of worked casts.