The juvenile stages of some insects, for example, have completely different kinds of mouths than their adult versions, like caterpillars, which use chewing mouthparts to devour leaves before metamorphosing into butterflies and moths with siphoning mouthparts.

例如许多昆虫的幼虫时期有着和成年时期完全不同的口器类型，比如毛虫在变成蝴蝶和飞蛾之前会用咀嚼式口器来吞食叶子，而蝴蝶和飞蛾则是虹吸式口器。