Genus Lethierium Dlabola, 1980

Lethierium Dlabola, 1980: 235 .

Type species: Hysteropterum reiberi Lethierry, 1878, by original designation.

Diagnosis. Metope wide, often smooth and without carinae. Coryphe transverse. Forewings wide, with wide hypocostal plate. Hind wings rudimentary. Abdominal sternites IV–VI in imago each with two large sensory pits medially. Phallobase strongly curved, its proximal part (basement) with a pair of lobe-shaped processes.

Supplementary description. Eyes large, 0.5 as wide as coryphe (in dorsal view). Coryphe transverse, with lateral margins weakly diverging anteriorly (Figs 1, 6, 9, 12, 16, 21, 31, 40, 55). Metope wide, often smooth and without carinae (Figs 3, 8, 11, 14, 20, 30, 39). Coryphe and metope joint at obtuse angle (in lateral view). Ocelli absent. Postclypeus smooth, without carinae. Rostrum reaching hind coxae; 3 rd segment narrowing apically, slightly shorter than 2 nd one. Pedicel globular. Pronotum with strongly convex anterior margin and nearly straight posterior margin. Paradiscal fields of pronotum wide behind the eyes. Paranotal lobes of pronotum wide, without carine, with slightly bent lower margin (Fig. 54). Forewings wide, extend beyond the abdomen apex, with weakly obtusely angulate costal margin and distinct membrane (Figs 2, 7, 10, 13, 17). Forewings often with distinct shoulder-shaped prominence (or knee prominence) well recognized as bulge at first furcation of radius (Fig. 12, kp). Forewings with wide precostal area and wide hypocostal plate, basal cell small. Clavus long, ⅔ of wing length. Hind wings rudimentary, nearly reaching abdomen basement (Fig. 22), matte. Hind tibia with 1–2 lateral spines. First metatarsomere short and wide, with two latero-apical and 6–7 intermediate spines in continuous row. Second metatarsomere equal in length to first one, but narrower, with only two latero-apical spines. Ventral surface of first and second metatarsomeres with long setae.

Abdominal sternites IV–VI of imago each with two large sensory pits medially (Figs 4, 5). Each pit comprises of wide circle depression of the cuticle with a sensory hair in its centre arising from dark brown socket, laying nearly horizontally and directed to the rim of the depression at acute angle to the midline of the sternite. Besides these large sensory pits the sternites IV–VI have also several trichobothria, from three to seven on each side along its posterior margin, which are represented by long sensory hair (longer than surrounding setae) arising from dark brown socket vertically from the cuticle.

Male pygofer elongate vertically, with weakly obtuse or nearly right upper angle and nearly straight hind margins (Figs 23, 32, 41, 47, 56). Lateral margins of anal tube turned downwards (25, 38, 57). Phallobase strongly curved, with a weakly sclerotized sac dorso-apically, its basement with a pair of lobe-shaped processes (Figs 26, 34, 46, 49, 59). Dorsolateral phallobase lobes narrowing apically, without processes. Ventral phallobase lobe long and wide, narrowing apically (Figs 27, 33, 45, 50, 61). Apical aedeagal processes not visible above the phallobase, narrowing apically. Aedeagus with a pair of ventral hooks, often strongly curved. Style with well developed apical and lateral teeth (Figs 29, 35, 43, 51, 62). Connective with a large cup (Figs 26, 34, 46, 49, 59, 60).

Hind margin of female sternite VII widely concave (in ventral view), with labial median process (in dorsal view) (Figs 64–68, 70). Gonoplacs convex, without carinae (Figs 19, 71). Gonocoxa VIII with weakly lobe-shaped hind margin (Fig. 74). Anterior connective lamina of gonapophysis VIII wide, with three teeth in apical group and 3–4 teeth in lateral group. Endogonocoxal process slightly furcating apically (Fig. 75). Posterior connective laminae of gonapophyses IX vertically elongate, with its distal parts curved at obtuse angle (Figs 72, 73, 76, 77). Median field of the laminae two-lobed (Fig. 73). Lateral fields of the laminae short. Gonospiculum bridge large.