These small moths come in a diverse range of more or less subdued colors and in their natural range can usually be distinguished by their wing venation: In the forewings, vein 1b is forked and vein 1c missing; veins 2 and 3 neither run parallel nor approach at the end, and vein 5 does not emerge from a common stalk with veins 6-8. In addition, like in some related moths the scape is short and bears a comb.[1]
The male genitals are generally similar to those of cosmet moths, but this may be a symplesiomorphy. The vinculum is variously developed and the valvae thus attach variously far from the tegumen, though often quite closely. The gnathos is typically two-armed, but one of the arms may be underdeveloped or even missing altogether. The right manica is vestigial or missing, while the left one is set tightly against the aedeagus. Most characteristically though, the eighth sternal and fourth to seventh abdominal segments are modified, the former forming epitygmata ("genital flaps"). Like in some related moths, the males also have a tuft of hairs on the hindwing underside, which can be folded into a pocket in the wing cell. The uncus (in males) and signum (in females) are usually absent. As regards other features of the female genitals, the ovipositor is long while the ostium is usually well sclerotized and protrudes, but may be recessed into a deep pit in the seventh sternal segment.
Clarke, John Frederick Gates (1986): Pyralidae and Microlepidoptera of the Marquesas Archipelago. Smithsonian Contributions to Zoology416: 1-485. PDF fulltext (214 MB!)