Idionychidae

Wing venation : Forewing midbasal space without crossveins and with a single cubito-anal crossvein. The sectors of the arculus are fused for more than half its length in at least one wing pair; supertriangles are crossed, triangles are free, and the anal loop is elongate with a gently curved midrib. Adult morphology : Adults have a slender abdomen without distinct lateral carinae. Males possess spined auricles, a keeled protibia, short hooked metafemoral spines, and highly variable anal appendages. Male accessory genitalia : The genital lobe is large, while the anterior hamule is strongly reduced. The posterior hamule is distinctive, with a sharp ventromedial branch and a broad, blunt dorsolateral branch. Female morphology : Both pairs of gonapophyses are short or reduced. The vulvar lamina lacks a median cleft and does not project ventrally; some species may possess horn-like processes on the vertex. Vesica spermalis : The vesica spermalis has a curved, flattened ligula, long curved cornua, two flagella, and reduced or absent lateral lobes. The terminal segments vary considerably among species. Larva : Larvae have broad, setose labial-palpal teeth, divergent wing pads, plate-like prothoracic epaulets, and a shelf-like frontal prominence. Dorsal abdominal hooks are absent, while lateral spines are restricted to S8–S9.