Mantises have a number of enemies, particularly birds. In order to discourage them, large mantises will strike out with their spiny forelegs. Other species, not large enough to frighten an enemy in this way, seek to discourage an aggressor by suddenly exposing brightly colored wings, which often have false eye-spots to give the impression of a frighteningly aggressive face. Such tactics are only necessary when the mantis has actually been seen. The first line of defense is to avoid detection at all. Most mantises are therefore well camouflaged for its survival, to avoid been eaten by birds. Grass-dwellers tend to be green, and tree-dwellers are often mottled brown.