In the phylogenetic classification of the Lepidoptera, the position of the genital opening and its modifications help to clarify the relationship of the Zeugloptera to the lepidopterous suborders. Three different systems of the suborder classification of the Lepidoptera, into Homoneura and Heteroneura (Tillyard, Imms, etc.), Monotrysia and Ditrysia (Borner), and Dacnonypha, Monotrysia, and Ditrysia (Hinton), are not supported by evidence obtained in the study of the female genitalia.The development of the female terminalia is closely associated with the mode of oviposition. Several types of female terminalia are found in the primitive Lepidoptera (Hepialidae, Neopseustidae, Tischeriidae, Lyonetiidae, Agathiphagidae, Tineidae, Nepticulidae, and Eriocraniidae). They are divided into four categories: hepialid type — the eggs are dropped randomly; typical lepidopterous type — the eggs are laid on the surface of food plants; eriocraniid type — the eggs are laid inside the food plants; tineid type — the eggs are laid in crevices of food. Each of the types is derivable from the types occurring in Neopseustidae, Tischeriidae, Agathiphagidae, and Eriocraniidae, respectively. These types are still far removed from the type of female terminalia in Micropterygidae of the Zeugloptera.The modes of egg-laying as well as the morphological characters of the female genitalia must be taken into consideration in suborder classification of the Lepidoptera.A genealogical tree based on the female terminalia suggests four main branches: hepialid branch — includes Neopseustidae and Prototheoridae; typical lepidopterous branch — includes all Ditrysia and Nepticulidae; tineid branch — includes only Tineidae; eriocraniid branch — includes Incurvariidae, Prodoxidae, Adelidae, and Heliozelidae.