Two woodlice

[Toby]

I know the grey one is a Common Rough Woodlouse - what is the brown one or is it just a younger version of the same?

[Pudding4brains]

Howdy,
Porcellio scaber is much, much more colourful than people think. The forma typica is the grey one on the bottom, but colour varieties range from plain bright orangy-red, to speckled yellowish-white, speckled orange-brown to the quite frequent "brown with orange rim" of the top one in your image. Some varieties (notably the "bright" yellow and orange speckled ones) only occur in females.

So, although the top one is smaller, and hence might very well be a tad younger (not necessarily though!), being younger is not the reason for the differing colour on that one. Having said that, very young P. scabers (and in fact most species of woodlice) are much lighter coloured - they are "born" entirely colourless (translucent white) and slowly acquire their colour during the first months of their lives. Your top one is way past that though.

Cheers! Arp
P.S. Here's a fairly typical colony showing some of the frequent colours.

[Toby]

thanks for info.