Infra-order Brachyura, Family Grapsidae

Grapsus crab | Grapsus tenuicrustatus​  Herbst, 1783 ​

Christmas island crabs, grapsus crab, grapsus tenuicrustatus, Christmas Island, crab, Max Orchard

The greenish “rock-hopping” crabs present in high numbers around the island coastline. Has a flat, thin disc
like carapace up to 65–70 mm wide. Body coloration varies widely from dark blue-green to light streaked brownish. Legs usually reddish brown marbled with green. Claws and face reddish. Also known as Spider crab, Sally-lightfoot crab or Rock 
crab in other areas of their range.

Read more about Christmas Island's grapsus crabs in the book

"Crabs of Christmas Island" by Max Orchard

Christmas Island crabs, crab, Christmas Island, grapsus crab

Grapsus crab