manjushra asks if I can identify this story. I can't, so I turn it over to the collective wisdom of Livejournal:
Genre: Sci-fi, feminist, could be authored by Sheri Tepper although I have read all the synopses I can find of her major works and it doesn't seem to be there.
Imagine the scene: we are a human-like (possibly human) race on an alien planet, but we've been here for ages and lost touch with the technology that brought us here. That's all a dim legend. We live in cliffs, in tunnels and holes we dig/bore. There are some strange taboos and real dangers: never leave the cliffs/go outside at night, don't ask questions about girls who go missing.
Cutting to the chase: the plot centres around the revelation of an obscene coming-of-age ceremony for girls, where they are chained down outside the cliffs and left to the mercy of the rather horrible flying/insectoid? aliens.