New records are listed. The following new species are described: Aleuropteryx cupressi (U.S.A.), A. longipennis (U.S.A. & Mexico), A. punctata (U.S.A. & Mexico), Neoconis bifurcata (U.S.A.), Coniopteryx (Coniopteryx) californica (U.S.A.), C. (C.) mexicana (Mexico), C. (C.) simplex (U.S.A.), Semidalis deserta (U.S.A.) and S. frommeri (U.S.A.). Several species are recorded for the first time from a country: Aleuropteryx unicolor Meinander, Coniopteryx minuta Meinander and Semidalis flinti Meinander from Mexico, Helicoconis similis Meinander and Coniopteryx palpalis Meinander from the U.S.A. and Helicoconis lutea Wallengren from Canada. The female of the Canadian H. lutea is brachypterous ; the specimens were collected from high altitude tundra. The genitalia of the following females are figured for the first time: Aleuropteryx cupressi sp. n., A. punctata sp. n. A. simillima Meinander, A. unicolor Meinander and Neoconis marginata Meinander.