Domestic beasts: the woodlouse

posted in: Natural Word | 3

Did you know that however far inland you may live in the UK, you share your property with crustaceans?

Drawing of three adult woodlice and a baby by Rowena Millar
Some woodlice … including a youngster. Drawing © Rowena Millar

Woodlice are isopods, which are crustaceans just like lobsters, crabs and shrimps. They originally came from the ocean, where marine isopods (some looking a lot like garden woodlice) can still be found. Look on the rocky shoreline for the sea slater – it’s the UK’s largest terrestrial isopod and the only seashore version that’s able to wander around breathing air. My pond is full of freshwater shrimps too.

These little grey things were a feature of my childhood and probably yours too – crawling around like little armadillos, falling off things and getting tipped upside down, wiggling pale little legs as they struggle to right themselves. Their general familiarity has led to quite fond nicknames, apparently such as chiggy pig in Devon, where I spent my formative years, and gramersow across the border in Cornwall, where I have spent the larger part of my life.

The sort that roll into a ball always surprise me, as the ones I usually see are not all that bendy and simply don’t do this. They are also less waxy. Maybe the shiny pill bug sort are a little safer from the centipedes, toads, hedgehogs and shrews on the lookout for woodlice during their nocturnal forages, in addition to its own bespoke predators, the woodlouse spider Dysdera, and the parasitic woodlouse fly. Apparently the woodlice that avoid these foes can live for four years.

Like its relative the sea slater, the woodlouse uses adapted gills for breathing air. These are fed by gases in the blood as if they are lungs, but instead of being in the chest, they are underneath and at the back, on modified hind legs. The gases diffuse through water and this is why woodlice need dampness to survive. However, their armour is not waterproof and a real soaking, as well as drying out, can kill them.

So next time you see a woodlouse, take a little time to look more closely. There are 35–40 different UK species to find, and about 3,500 woodlouse species throughout the world, so plenty to keep a woodlouse twitcher busy looking under logs and flowerpots for a long time!

3 Responses

  1. R Gelling

    The woodlice of my childhood in the Chilterns were all the “roll in a ball” type. The soil was chalky which must have suited them. I expect that you know that they were given as a medicine coated in sugar and honey, hence the name “pill bug”

    • admin

      Dear Rosalie,
      According to Wikipedia:
      “British Isles
      Of these 45 species, only five are common: Oniscus asellus (the common shiny woodlouse), Porcellio scaber (the common rough woodlouse), Philoscia muscorum (the common striped woodlouse), Trichoniscus pusillus (the common pygmy woodlouse), and Armadillidium vulgare (the common pill bug).
      Kingdom: Animalia
      Suborder: Oniscidea; Latreille 1802
      en.wikipedia.org › wiki › Woodlouse”

      Here are some links with pictures. Do you recognise any woodlice from your childhood?
      https://www.uksafari.com/woodlice.htm
      https://www.naturespot.org.uk/taxonomy/term/19555

      Yes, I had heard about the ‘pill’ bugs. Apparently they are quite nutritious ….

      Best wishes
      Rowena

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