ID this crab - SPS pest

[ReefWreak]

Can anyone provide an ID for this fella who I spied crawling around my birdsnest tearing vigorously at something on that coral (probably polyps). I've never seen his ugly self before, and don't want to again. I took a bunch of flash pics, stunned him with the flash, grabbed with the tongs, and put him in an isolation bucket hanging from the top of the tank. Any idea of his intent and who he may or may not be would be very helpful. I'll drop some pics in the other invert forum and see if they want any samples of him sent, although he's probably squashed in half now, and I don't know where my liverock came from.

Thanks in advance!

http://i15.photobucket.com/albums/a373/ericzombie/uglymofo3.jpg

http://i15.photobucket.com/albums/a373/ericzombie/uglymofo2.jpg

http://i15.photobucket.com/albums/a373/ericzombie/uglymofo.jpg

[Frick-n-Frags]

give him a tiny piece of the birdsnest and see if he totally devastates it. I would, because if he was cleaning it, he wouldn't eat the little piece, maybe just work it over, but if it is polished off, there you go, he definitely needs to go

[Moonstream]

he looks like a decorator crad to me. some people call them spider crabs. try typing in decorator crab in on google images. could you get a better pic maybe?

[ReefWreak]

I looked this morning at the area where he was on the birds next and there are a bunch of polyps that are white or white holes in the birdsnest... so that narrows down what he was doing up there. If I were to give him the benefit of the doubt, I could say that maybe he was grabbing on there when I yanked him off, however I just don't think that would be quite accurate...

[Travis L. Stevens]

It looks like a Majidae of some sort. Resembles a decorator crab really well.

[Paintbug]

decorator crabs are known to yank off polyps to use as camouflage. honestly the loss of a few polyps is worth it to see one of those crabs in the tank. they can be destructive, but very interesting creatures to say the least.