Alien Invader? Nope - Giant Coconut Crab.

Okay, you know what? If I go to carry my garbage out to the curb and encounter this thing clinging to the side of my garbage can? I'm calling the National Guard, because I'll be pretty sure we've been invaded, Independence Day style. Don't even try to tell me you don't see the similarities... Giant Coconut Crab

It's alternately called a Christmas Island Robber Crab, Palm Thief crab, or Giant Coconut Crab. The photo is from an email reportedly sent to Snopes.com where they've done an entry about whether or not this is a real critter instead of a photoshopped monstrosity/hoax. The verdict? The coconut crab really is the biggest land-dwelling arthropod in the world. I can see why they call it a Palm Thief in some countries—the thing is very nearly big enough to carry off your trees.

They also apparently have a penchant for swiping shiny objects. They'll supposedly steal bright things like tableware, watches, or jewelry from campsites and yards. Also called the Palm Thief (See? This one has been caught in the act...)

These crabs can't swim once they're out of their larval state, and they breathe by means of an organ that's something like a cross between gills and lungs, called a branchiostegal lung. Coconut crabs are essentially a kind of giant hermit crab, (err...sort of.) They're primarily nocturnal, so I can't imagine why the big guy up above is committing his daring daylight raid on the garbage can.

If, like me, you have a soft spot for gigantic, non-venomous earth animals with exoskeletons, check out Hugecrab.com, where they've collected and captioned a great many pictures.