The 'common-or-garden' earthworm Lumbricus terrestris (sometimes called the lobworm) is probably the most familiar (it's the one we study at school) and is what is often being considered when we talk about 'earthworms' in a general way. It is the largest red earthworm in the UK and is often found when digging in gardens or grasslands. Although it's also found in orchards, it is less common in woodlands, farmland and near rivers - other species take over in these habitats - and it isn't even our most common species, even if it the most familiar; that honour may go to the 'grey worm' Aporrectodea caliginosa. Britain has around 45 species compared with 180 in France - the English Channel is a real barrier if you can't fly or swim.
Much is written about L. terrestris so I won't repeat it here - instead I want to look at two rather distinctive species. The first of these is the manure worm (AKA brindling or brandling) Eisenia fetida which is up to around 120mm long.
|A pair of Eisenia fetida mating|
|Close-up of the joined clitellum ('saddle') regions of mating Eisenia fetida. Note how the clitellum is wide and almost encircles the other worm.|
The second species, the 'green worm' or 'stubby worm' Allolobophora chlorotica is very different.
|Allolobophora chlorotica in garden soil.|
This has been a very quick look at just two species, but they are both common and distinctive, so I hope you'll look for them as they go about their essential business, and maybe look out for some other species too. Enjoy!
There are plenty of gardening and allotment books that talk about earthworms in general, but I think a good one is:
Morgan, J.A.. (2004). Earthworms, Nature's Gardeners. Osmia, Rothley.
If you want a technical guide to British earthworms, there's really only one title to go for:
Sims, R.W. & Gerard, B.M. (1999). Earthworms. Synopses of the British Fauna (new series) (revised) 31: i-viii, 1-169.