We all know a woodlouse when we see one, but did you know that there are more than 20 species recorded in Guernsey?

How many have you seen? Have you notced that there are different species? Not many of them have common names, those which do are the more regularly seen ones.

The most common species locally are Porcellio scaber, the common rough woodlouse, which comes in a variety of sizes and colours which doesn't help the newcomer to woodlouse identification, but as you get used to it they come a lot easier and the ID points follow easily for the more common ones.

What do you need to look at to work out the species?

• The Antenna - the whole shape and size plus the number of parts to the end section (flagella).
• The Telson and Uropods (their back end).
• The general shape. Is the tail (Pleon) narrower than the body (Pereon) giving a stepped body outline.
• Colour and pattern can be important in some species but many are quite variable.
• Habitat. This is proving to be a little confusing in Guernsey as so many habitats cross over within a few hundred feet of each other.
• Lungs, if you flip a woodlouse upside down, you can see the white lungs of some species, the number of pairs of lungs is an identifier for some species.
• Eyes - Do they have eyes? If they do (some are blind), how many ocelli make up the eye, what colour are the Ocelli?
• Size - Some are only about 2mm long as adults where the Porcellio scaber can get up to around 18mm.
• Hair/bumps - some are hairy, some are covered in bumpy tubercles, some are smooth.