Psilotreta bitubercula sp. nov.

(Figs 7A–7G, 11E)

Diagnosis. The male of this species is very similar to that of P. flavida, but is easily distinguishable from the latter by the shape of the median dorsal process of tergum X. A pair of small tubercules are present apicoventrally in this species (Figs 7A, 7B), but are lacking in P. flavida . The female of this species is also very similar to that of P. flavida but can be distinguished from the latter by having a pair of dark bands on sternum IX in ventral view (Fig. 7G).

Adult. General coloration pale brown in body, antennae and wings (in alcohol). Length of each forewing: male 6.0– 6.2 mm (mean = 6.1, n = 2), female 6.1–6.5 mm (mean = 6.26, n = 5). In head, thoracic nota, and venation, general morphology most similar to P. flavida (Figs 8A–8C), but in each female forewing, M3+4 and Cu1a connected by short crossvein m-cu in P. bitubercula sp. nov., same as P. atrocaudata sp. nov. (Fig. 5A) (those veins directly connected with each other without crossvein m-cu in P. flavida as in Fig. 8C)).

Male genitalia (Figs 7A–7E). Tergum IX subtriangular in dorsal view, with steep sides above rounded basal setal warts (Figs 7A, 7C). Basal segment of each inferior appendage long, extending beyond posterior of lateral processes of tergum X, cylindrical and covered with setae, tapered (Fig. 7C); apical segment about 1/3 length of basal segment, cylindrical, with many brown teeth on apical half. Preanal appendages oval and tapered apically in lateral view (Fig. 7C), extending to posterior margin of median dorsal process of tergum X in dorsal view (Fig. 7A). Tergum X bears median dorsal process heavily sclerotized dorsally and laterally, thick, turtle-head shaped in dorsal view (Fig. 7A), sparsely setose apically, with pair of small setose tubercules apicoventrally (marked with arrow in Fig. 7B); lateral processes each with long, acute ventral projection angled posterad (Fig. 7C); pair of intermediate appendages heavily sclerotized, sharply curved posteroventrad, forming C-shaped in lateral view, positioned on lower 2/3 of each lateral process (Fig. 7C).

Phallus with phallotheca short, cylindrical; endotheca with pair of short and thick parameres located lateroventrally, each about 3 times as long as its basal width; aedeagus membranous with ventral plate weakly sclerotized, phallotremal sclerite distinct V-shaped in ventral view, strongly C-shaped in lateral view (Figs 7D, 7E).

Female genitalia (Figs 7F–7G). Sternum IX semicircular with pair of dark bands in ventral view (Fig. 7G). Segment X bilobed in dorsal view, each round lobe setose (Fig.7F). Vaginal apparatus almost 2 times as long as sternum IX in ventral view (Fig. 7G).

Larva. Unknown.

Holotype. Male (in alcohol), Amami Island, Yakugachi-gawa, Sumiyo-cho, Amami-shi, Kagoshima Pref., Japan, 33°45'N, 133°11'E, 23.vi.2007, M. Takai. (LBM1410012577).

Paratypes. Amami Island, 2 females, same locality as holotype, 23.vi.2007, M. Takai (LBM1410012578 – LBM1410012579); 1 male, 1 female, same locality, 24.vi.2007, M. Takai (LBM1410012580 – LBM1410012581); 1 female, same locality, 24.vi.2007, M. Takai. (LBM1410012583) .

Etymology. The species name “ bitubercula ” refers to two tubercules on the apical part of the median dorsal process of segment X in the male genitalia.

Distribution and habitat. Psilotreta bitubercula sp. nov. is an Oriental species distributed on Amami Island in the Ryukyu Archipelago, southwestern Japan (Fig. 11E). All specimens used in this study were collected streamside by light traps.

Japanese name. Futakobu-kiso-tobikera