Adults of two coniopterygid species, Aleuropteryx juniperi Ohm, 1968 (Aleuropteryginae) and Semidalis aleyrodiformis (Stephens, 1836) (Coniopteryginae), were studied using scanning electron microscopy. Interspecific differences in the ultrastructure of the integument of all the major parts of the body were identified and described, and the functional and phylogenetic implications of the differences discussed. Additionally, the enlarged terminal segment of the labial palps of the Coniopterygidae and the Sisyridae, which up to now has been used as an argument for a sister-group relationship between these two families, was subjected to a thorough comparison. The very different morphology makes independent enlargement of the terminal palpal segment in both families plausible. This finding is congruent with the earlier hypothesis of a sister-group relationship between Coniopterygidae and the dilarid clade, which was proposed on the basis of molecular data, larval morphology and male genital sclerites. Finally, a new classification of the coniopterygid subfamilies is presented based on characters of the larval head (prominence of the ocular region, relative length of sucking stylets). The following relationship is hypothesized: (Brucheiserinae + Coniopteryginae) + Aleuropteryginae, and the implications of this hypothesis for the phylogenetic interpretation of the ultrastructural differences that we found are discussed: (1) The wax glands, as well as plicatures, are interpreted as belonging to the ground pattern of the family Coniopterygidae, and (2) the wax glands are considered to have been reduced in Brucheiserinae and the plicatures in Coniopteryginae. A distinct (though reduced) spiraculum 8 was detected in Semidalis aleyrodiformis; as a consequence the hypothesis that the loss of spiraculum 8 is an autapomorphy of Coniopteryginae is refuted.