Plethus Hagen

Ito, Tomiko & Saito, Rie, 2016, First record of Plethus Hagen (Trichoptera, Hydroptilidae) from Japan, with description of a species, Zootaxa 4154 (4), pp. 466-476 : 467-468

Genus Plethus Hagen

Plethus Hagen, 1887 , 643. Type species Hydroptila cursitans Hagen , by monotypy.

Adult (modified after Marshal 1979; Malicky 2010). Head with pairs of large semi-ellipsoidal dorsal warts and posterior warts. Ocelli 3. Antennae 18–19-segmented. Maxillary palpi each 5-segmented, 2 basal segments short, other segments cylindrical; labial palpi each 3-segmented, basal segment short, other segments cylindrical. Pronotum with both pairs of mesal and lateral warts round; mesoscutellum triangular without middle transverse line; metascutellum rectangular. Wings black, apically acuminate, densely covered with long black hairs, venation rather reduced especially in hind wings. Spur formula 0-2-3, 0-2-4, or 1-2-3. Abdominal segment VII without ventral process. Genitalia relatively uniform in appearance with long anterior apodemes.

Larva (modified after Ulmer 1957; Marshal 1979; Wells & Huisman 1993). Body depressed, flattened dorsoventrally. Prosternum with pair of transverse sclerites posteriorly. Dorsal sclerites of abdominal segments I– VIII wide. Posterior margin of dorsal sclerite of segment IX simple without sculpture.

Case (modified after Ulmer 1957; Marshal 1979; Wells & Huisman 1993). Depressed, dorsoventrally flattened, dome-shaped and made of silk.