NATURE NOTES WHY, I wondered, is the inside of the lid of my Dalek-type compost bin thick with earthworms?
When I remove the lid the worms either plop back inside or make a break for freedom down the outside of the bin, or drop onto the ground. Hundreds of them.
When I set up the bin I made sure it was standing on bare earth and then added a layer of rotted horse manure — always a good source of earthworms, which are essential to convert the garden and kitchen waste into soil enriching compost.
The worms have multiplied and are certainly doing their job, as the waste rots down very quickly in these plastic drums — much faster, it seems to me, than the heaps I used to build which were held together by wooden slats.
There are 26 British species of earthworm varying in size from 6cm to about 30cm long, and they range in colour from a dark red to pale yellow/green. The different types of earthworm are not easy to tell apart, but one group — the litter dwellers — are the most distinctive, living either in the leaf litter at the soil surface, or within compost heaps; they have dark red or brown colouring and in the case of the tiger worm (Eisenia fetida) a set of distinctive stripes.
Charles Darwin's last book, published in 1881, was dedicated entirely to exploring earthworm behaviour and ecology, and continued the theme common throughout his work that gradual changes over long periods of time can lead to large and sometimes surprising consequences.
And at one point he draws on the observations made by his son, William, who visited the newly excavated Brading Roman Villa and speculated about the effect of earthworm activity on the burial of archaeological remains.