There are 37 species of native or naturalised woodlice in Britain And Ireland, and they are one of the most common and widespread animals which although familiar are mostly ignored. They are quite a diverse group, and are members of the class Crustacea, which also includes crabs shrimps and lobsters. There are around 10,000 species of Isopoda worldwide, most of which are marine.
Woodlice are often considered as pests in gardens and greenhouses, and when they enter houses. They are completly harmless, and although they may nibble on the odd tender seedling, they play a very important roll in recyling and the enrichment of soil in ecosystems, especially woodland. They feed mainly on dead plant matter like leaf-litter and rotting wood, which in digestion is turned into nutrients, and with the help of fungi helps speed up decomposition and fertilises the earth. Woodlice are also a good food source for birds, frogs, toads, shrews, spiders, centipedes and other predaceous invertebrates.
Of interest, throughout history woodlice have appeared in recipes and cures, one such recipe was for a woodlouse sauce.
For further reference and with help and thanks for confirming identifcation of some of the more challenging species see the links below.
British Myriapod and Isopod Group (BMIG) – Promoting the study of Centipedes, Millipedes and Woodlice in Britain and Ireland. It aims to actively develop identification, training and recording relevant to improving the knowledge and conservation of centipedes, millipedes, pauropods & symphylans (the Myriapoda) and woodlice & waterlice (the Isopoda) found in Britain and Ireland. The group is responsible for three National Recording Schemes, one each for centipedes, millipedes and woodlice & waterlice.
Facebook Isopods and Myriapods of Britain and Ireland Group – It is for anyone interested in the study of Isopods (marine, freshwater and terrestrial) and Myriapods (Centipedes and Millipedes) in Britain and Ireland. Post your photos, ID questions, news etc.
iRecord – iRecord is a website for sharing wildlife observations, including associated photos – you can register quickly and for free. Once you’ve registered, you can add your own biological records for other to see, and you can see what has been recorded by others. The goal of iRecord is to make it easier for wildlife sightings to be collated, checked by experts and made available to support research and decision-making at local and national levels.
NBN Atlas – The NBN (National Biodiversity Network) Atlas is an online tool that provides a platform to engage, educate and inform people about the natural world. It will help improve biodiversity knowledge, open up research possibilities and change the way environmental management is carried out in the UK.
An AIDGAP publication A Key To The Woodlice of Britain And Ireland is also a very good reference.