Menaethius monoceros is known as spider crab and decorator crab because it looks like spider and likes to decorate itself with materials from the external environment. It has a single rostrum at the front of its carapace, which gives its name monoceros.  It is well adapted to a lot of different marine environment and distributes widely in the Indo-Pacific area. And because of its successful adaption, it is a very important species in the ecosystem.