Very large woodlouse

[Bruce Williams]

Stony Stratford, Bucks.

This is probably the largest woodlouse that I've ever seen (or noticed anyway) measuring the best part of 20mm long. It was very impressive!

I'm guessing that it's probably just an extra large specimen of one of our common species, however I'd appreciate cofirmation of id and comments views on it's large size.



Bruce

[Jason Green]

Hi Bruce,

We have about 35 species of Woodlouse in the UK and some I don't doubt are superficially similar and need a dead individual keying out for certainty. However, from what I can see it looks like Oniscus asellus - indeed common.

Take care,

Jason

[aeshna5]

Agree it looks like Oniscus asellus, one of the commonest garden woodlice.

[Vincent86]

Yes it does look like Oniscus asellus. It is is one of the largest and most common species of woodlouse in the British Isles and Western and Northern Europe, growing to lengths of 16 mm and widths of 6 mm. You say it's 20 mm? Quite large.

[Jason Claxton]

A nice cheap book for these Bruce is:- A key to the Woodlice of Britain and Ireland by Stephen Hopkin in the FSC AIDGAP series,it has some very useful pictures in it too ,so dont be put off by the "key" part.

[Bruce Williams]

Thanks for your help guys.

Yes I thought it might be one of our common species, my posting was more based on its unusually large size (length rather than width).

Vincent - Size was estimated against my thumbnail, so my "...best part of 20mm" could mean it was a little less. However I'd be surprised if it was less than 18mm.

Two possibilities occur to me:

From the photo it seems very "stretched out" with gaps between every segment. I don't know for sure why this should be (full of eggs maybe?) but it might account for its atypical length. Compare the segment gaps with these individual from my earlier Gallery postings:



Look particularly at the insert in my annotated image.

In most species (including humans) unusually large specimens occur from time to time.

Bruce