The mouth parts of these primitive moths 'adult forms still include functional chewing mandibles, rather than the sucking proboscises of other moths. They evolved from earlier trichopteroid insects (caddis flies), and have retained the latter's mouth structures.
小翅蛾、卵翅蛾的成蟲，長著齒狀的咀嚼式「嘴巴」，與其他蛾類吸式狀口器不同，它們由演化上更早的毛翅群進化而來，卻保留了原有的器官。