Wednesday, 19 March 2014

Woodlice - for William

Woodlice are crustaceans, so they are close relatives of prawns and crabs. Most crustaceans live in the sea so they never dry out. Woodlice live on the land and have to be very careful not to get dry or they can quickly die. 

Armadillidium vulgare from beneath a stone.
Pit Lane, Byfield. 19 March, 2014

Some can roll up into a ball and this helps the delicate parts of their bodies to stay damp. The picture shows the common "Roly-poly" (it has lots of name) which I found under a stone, but this species will often come out in fairly bright sunshine.

They have no lungs, but if you turn a woodlouse upside down and look near its tail end you will see some white patches; these are little pads of tissue which can absorb oxygen and do the same job as lungs. These pads must stay damp because if they dry out they can't work, and the animal dies. This is why they stay under logs, stones or dead leaves.

The commonest woodlouse is Porcellio scaber or "scabby little pig". I wrote a bit more about this in my blog for 23 January, 2013 called "Roly-polies and Scabby little pigs".

I looked through my old photographs and found this picture of Porcellio scaber.  This species of woodlouse often gets into houses and I found this one in our kitchen! Oniscus asellus is similar but is bigger and rather shiny.

Sometimes, when you turn over a stone, you will find an ants' nest. Look carefully and you may find some strange little woodlice called Platyarthrus hoffmannseggi (sorry, this species doesn't have a common name). It is completely white and has no eyes. It lives all its life underground with the ants so it doesn't need eyes or body colour. It is common and even lives in my back garden.

Platyarthrus hoffamanseggi in my back garden.
17 March, 2014

It is rather small and I found it difficult to get a good photograph. In my garden it is living with black ants but it is more commonly found with yellow ants. 'Platyarthrus' comes from the Latin words for 'flat joint' (your Mum knows all about arthritis because she worked with patients who had joint problems).

Most woodlice are rather dull but if you are lucky you may find a lovely one called the Rosy Woodlouse. It is a bright pink species with a pair of yellow stripes down its back. It lives under damp leaves but for some reason I often find it under rather wet cardboard on waste ground. I haven't got a picture of it but there are plenty on the internet under its Latin name of Androniscus dentiger.

Keep looking, and good luck!


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