Genus Tsudaea gen. nov.

Type species: Brachycentrus kitayamanus Tsuda 1942 .

Diagnosis— The genus Tsudaea is generally similar to the genus Eobrachycentrus Wiggins in both adult and immature stages. The adults of Tsudaea have frons with a large central setal wart and a pair of large lateral setal warts (Fig. 1 B), but in Eobrachycentrus the frons has two pairs of lateral warts (Wiggins 1965, Wiggins et al. 1985). Males of Tsudaea are distinguished from other known brachycentrid genera by having distinct phallic spines (Fig. 2 E, F). The larval submental sclerites are fused into a single plate in Tsudaea (Fig. 3 C), but separated in Eobrachycentrus (Wiggins 1965); and a pair of abdominal gills are present in Tsudaea (Fig. 3 A) but absent in Eobrachycentrus (Wiggins 1965, 1996). The presence of lateral humps on the first abdominal segment is unique to larvae of Tsudaea . In the pupal stage, the posterior hook plate on the fifth abdominal segment shows a linear row of spines in Tsudaea (Fig. 4 A), but a more ovoid group in Eobrachycentrus (Wiggins 1965) . Pupal anal processes of Tsudaea are shorter (Fig. 4 A) than those of Eobrachycentrus (Wiggins 1965) . Cases are cylindrical and constructed of sand grains in Tsudaea (Fig. 4 C, D), but 4-sided and made from plant materials in Eobrachycentrus (Wiggins 1965, 1996).

Description— Adult (Figs. 1, 2, 8). Small, dark brown to black. Head without ocelli; with anterior setal warts oval, posterior and posterolateral setal warts slender; large round setal wart present on center of frons, with pair of large setal warts laterally; maxillary palpi 3-segmented and very short in male, 5-segmented in female. Both mesoscutal and mesoscutellar setal warts small, oval. Legs with tibial spurs formula 2, 3, 3 in both sexes. Venation with discoidal cell closed in fore- and hindwings of both sexes; venation of forewings similar in both sexes, with apical forks I, II, III and V; venation of hindwings with apical forks I, II and V in male, I, II, III and V in female. Abdominal sternite V with one pair of small scent glands near anterolateral margins in both sexes.

Male genitalia (Fig. 2 A–F). Segment X long, weakly sclerotized, with large strongly sclerotized intermediate appendages. Inferior appendages 2-segmented. Phallus with long spines at base of endotheca.

Female genitalia (Fig. 2 G–I). Sternite VIII large, tergum IX and segment X separated. Spermathecal sclerite simple.

Larva (Figs. 3 A–J, 9). Head flattened with distinct carina, ventral apotome longer than wide, submental sclerites fused into single plate. Prosternal horn absent. Pronotal sclerite with many, long, stout setae along anterior margin and transverse depression. Mesonotal sclerites with long, stout setae along anterior and posterior margins, each sclerite subdivided longitudinally. Metanotal sa 1 with single short seta, sa 2 and sa 3 sclerites with long, stout setae. Forelegs short, coxae with many, long setae, femora broad with teeth-like spines ventrally. Mid- and hindlegs slender with many, long setae. Abdominal segment I with pair of lateral humps. Abdominal segment II with pair of single gills. Lateral fringes present. Forked lamellae absent. Abdominal segment VIII with pair of protuberances dorsolaterally. Anal claw with two dorsal accessory hooks.

Pupa (Fig. 4 A–B). Labrum with five pairs of long, apically hooked setae, mandibles acute with many fine teeth on mesal margin. Tarsi of midlegs with dense fringe of setae. First abdominal segment with pair of spine-bearing ridges; anterior hook plates present on segments III to VII; segment V with two rows of spines posteriorly. Lateral fringe present. Abdominal gills absent. Anal process short with two apicomesal, long, apically hooked setae and with short thick seta apically.

Case (Figs. 4 C–E, 9). Cylindrical, constructed of sand grains and with pieces of moss and other plant materials attached.

Etymology. The genus is named in honor of the late Dr. Matsunae Tsuda, who was instrumental in the development of the study of Japanese aquatic insects. He described the type species of this genus in the first monograph of Japanese Trichoptera (Tsuda 1942) .