What is it?

[rfb3]

I have had my aquarium set up for about two months with mature live rock from a LFS. Just tonight I saw "rock dust" falling down the side of one of the rocks. I jumped up and saw what looked like hairy spider legs (or crab legs???) pushing "dust" out of a hole in the side of the rock.

Any guesses?

I'll try to get a pic... If this thing ever emerges.

Thanks,
Freddie

[elwaine]

It might be the Hairy Crab Pilumnus fissifrons (see: http://images.google.com/imgres?imgurl=www.museum.vic.gov.au/crust/images/crusties/brachyur1/j19511.jpg&imgrefurl=http://www.museum.vic.gov.au/crust/mov713i.html&h=293&w=450&sz=18&tbnid=PaJHp52o-2wJ:&tbnh=80&tbnw=122&prev=/images%3Fq%3Dhairy%2Bcrab%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DN, or it might be a hairy legged Emerald (Mythrax) crab. -- Just my guesses.