Exoporia are a group of primitive Lepidoptera comprising the superfamilies Mnesarchaeoidea and Hepialoidea (Kristensen, 1999; Nielsen et al., 2000). Exoporia is a natural group or clade which is the sister group of the lepidopteran infraorder Heteroneura. They are characterised by the unique female reproductive system which has an external groove between the "ostium bursae" and the ovipore by which the sperm is transferred to the egg rather than having the mating and egg-laying parts of the abdomen with a common opening (cloaca) as in other non-ditrysian moths, or with separate openings linked internally by a "ductus seminalis" as in Ditrysia (Nielsen et al., 2000). See Kristensen (1999: 57) for other exoporian characteristics.