Though these gowns retail for more than many American mortals earn in a year — that’s if they are put on store’s racks at all; most are snatched by stylists straight from designers’ ateliers — several stars conveyed earthy folksiness. “Apparently it took 30 people to make this in a week,” said a pregnant Keira Knightley of “The Imitation Game,” of her ruffle-trimmed, insect-printed Chanel frock. “What if I spill something down it or I rip it?” (Surely the large butterfly she wore on her wrist would slurp up any wayward nectar.) Kristen Wiig, a presenter, wore a white peasant dress by Delphine Manivet, and Ruth Wilson, of the Showtime series “The Affair,” wore a grassy-green Prada column with stripes thrown casually hither and yon. Lupita Nyong’o, in Giambattista Valli couture, looked like a lilac plucked out of a Mother’s Day bouquet.