Menaethius monoceros seems to be well adapted to a large variety of environment, as different samples were found in habitats like sublittoral mangrove shores (Cooper 1997), rocky shores (Jones cited in Cooper 1997) and sandy subtidal reef (Galil et al. 2011). It stays within the water depth of 0-90m (Griffin & Tranter 1974). However, it seems that the most important thing is the material on the surface of the habitat it lives in. Many studies have shown that there are usually sea weeds (Cooper 1997; Galil et al. 2011; Sankarankutty1965), algae, cyanobacteria mat (Cruz-Rivera & Paul 2006; Galil et al.2011; Simões 2001; Siokou 2013), sponge (Galil et al. 2011) and coral (Plaisanceet al. 2009). It is because M. monoceros usually uses these materials for decoration and the occurrence of these materials in the habitat makes the camouflage successful. Otherwise, it can also live in cloaca of some sea cucumber to seek protection (Stephesen 1945).