Walking with woodlice

The day started bright and warm, but I had my allocated wild slot in the early morning, so I decided to look and photograph some common woodlouse species. We tend to take these common invertebrates for granted, but woodlice are a diverse group with over 30 species in the UK with a range of habitat requirements, not all found on wood, and many species have quite restricted distributions. Five species are relatively easy to find and you are likely to have at least three in your garden, so my aim today was to find these common species.
  The Yorkshire Wildlife Trust's Wildlife Garden by Pearson Park was a good place to start, as Pill Woodlouse can reliably be found. And voila, a couple of Pill Woodlouse, Armadillidium vulgare, walking on the path greeted me, although they were in a bit of a rush and didn't stay around long. This species can survive in relatively dry habitats, and is not unusual to see it active in the open during the day. It can be found in sandy beaches, often under stones. Together with other related species it has the feature of being able to roll into a ball when disturbed, with its tough exoskeleton affording some protection to its softer underside.

Pill Woodlouse, Armadillidium vulgare, crossing the path at good speed

I then moved into the woodpile area. This is a shady, moist spot amongst trees. I looked under some logs and, squinting and getting really close I could see some Common Pygmy Woodlice, Trichoniscus pusillus. They are reddish and shiny, not very flattened and very tiny (up to 4 mm).

Common Pygmy Woodlice, Trichoniscus pusillus, on the underside of a log

 These little woodlice were in the company of the Common Shiny woodlouse, Oniscus asellus (above, one found under a brick) which looked like giants in comparison. This species reaches a maximum length of 16 mm, and are amongst the largest native species in the UK. The common shiny woodlouse is shiny and is quite flattened, mainly grey with paler patches and spots (where it stores calcium to form its exoskeleton).

 I went into a drier area, in the orchard, where there are loose bricks and pots over concrete. There I found one of the commonest species, the Common Rough Woodlouse, Porcellio scaber. It is a large species, slaty grey, with clear tubercles on its back. This species often forms large aggregations of various ages under logs, stones or bricks. This behaviour is thought to help reduce humidity loss.

Common Rough Woodlouse, Porcellio scaber, found under a pot

Under the same pot I found a Common Stripy or Fast Woodlouse, Philoscia muscorum. This species tends to have a dark head and a dark stripe along its back. It is quite colourful for a woodlouse and it keeps its body high when moving, which it can do quite quickly (hence its common name).

Fast Woodlouse, Philoscia muscorum, under a pot

That completes the group of common woodlouse species. But I had seen a few Rosy Woodlouse while moving some pots a few days ago. This is not very common, I tend to find single individuals under larger stones or under large pots that haven't been moved in a while, where there is enough damp organic material or mud. I thought I'd give it a try when I got back home. After lifting the pot and looking closely I did find a single one! They are 5 mm long, pink to orange, and have a yellow stripe on their backs and despite their size, quite obvious eyes. They have a rough surface, but my photo really didn't make them justice, see this one for a close look.

A Rosy or Pink Woodlouse, Androniscus dentiger, found under a large pot.

More Information

An identification key for the most common woodlouse species by the Natural History Museum, here.