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Help with identifying British woodlice, and why they are usually found huddled together in damp crevices.
Woodlice are land-dwelling crustaceans. They breathe through gills which need to be kept moist at all times, and this requirement influences much of their behaviour. It is easy to fall into the trap of thinking that woodlice ‘prefer’ damp, dark crevices – or, even worse that they ‘choose’ these places or ‘like’ them. This is falling into the trap of anthropomorphism – imagining that animals must experience the world as we humans do. In England students are often asked to write school reports about the behaviour of woodlice after carrying out experiments using ‘choice-chambers’. I have no intention of writing such a report here, but there is no harm in pointing out some common mistakes and giving a few ‘clues’. Woodlice are most active during the night and are usually found huddled together in damp places during the day, but they do not move towards damp conditions, it is just that they are more active in the dry. Similarly they do not choose crevices or other woodlice, but are more active when their bodies are not being touched. These differences in the levels of activity, and therefore rates of movement, mean that woodlice spend most of their time crowded together in damp crevices. This type, of behavioural response to stimuli is known as ‘kinetic’- it is not directional. The other error that students often make is to fail to mention the species of woodlouse they observed. ( Key to help Identify British Woodlice ). Woodlice are known as Sow Bugs in many parts of America, and a little more charmingly they are still called ‘tiggyhogs’ and ‘God’s Little Pigs’ in parts of Britain. One of the most familiar of the 37 British species is the Common Woodlouse (Oniscus assellus),and this one is now also found in the USA, having been accidentally introduced there by European settlers. Woodlice feed on dead plant material and are themselves preyed on by many garden animals, as well as by their own specialist predator – the Woodlouse Spider (Dysdera crocata). This spider is similarly widespread in Europe, and is another accidental introduction to the USA. It is quite a large spider, with a red thorax and brown abdomen. It has enormous fangs to pierce the woodlouse armour, and the ability to inject venom. This venom is not harmful to most humans, but beware – this spider will bite! So - avoid anthropomorphism when you write about woodlice and identify the species you study. Like this? – see what else I have written.
The copyright of the article Woodlouse behaviour in Other Invertebrates is owned by John Blatchford. Permission to republish Woodlouse behaviour in print or online must be granted by the author in writing.
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