Psilotreta japonica ( Banks 1906 )

Kawase, Naoki, 2022, The genus Psilotreta Banks (Trichoptera, Odontoceridae) in Japan, Zootaxa 5195 (6), pp. 501-521 : 502-504

Psilotreta japonica ( Banks 1906)

( Figs 1A–1K , 9B–9D, 9G , 10A, 10E , 11A )

Odontocerum japonicum Banks 1906 , 110, female, Honshu (Type locality: Gifu); Ulmer 1907a, 51–52, male, female, Honshu.

Psilotreta japonica: Ulmer 1907b , 126, wings of male and female; Tsuda 1959, 143, larva; Parker &Wiggins 1987, 34, male, female, Honshu; Tanida 2005, 556–557, male, female; Kawase 2012, 29–39, wings, male, female, larva, habitat, Honshu; Tanida 2018, 665–667, male, female, larva.

Psilotreta kyotoensis Iwata 1928 , 118, 125, larva, Honshu (Kyoto). Synonymized by Tsuda (1942).

Diagnosis. The male of this species can be easily distinguished from those of other Japanese species by the male genitalia: Each intermediate appendage is very short and needle-like in this species ( Figs 1D, 1F–1G ), but long and curved in other Japanese species. The female genitalia of this species are distinguished from those of other Japanese species by the shapes of paired pigmentations of sternum IX that are long triangular with the apexes directed posteromesad in ventral view ( Fig. 1K ). The larva is unique among known Japanese larvae in having a dark longitudinal median-band from the head to the mesothorax dorsally ( Figs 9B, 9D ), and in having many branches (more than 20 branches on each side of segments II–V) of the dorsal or ventral abdominal gills ( Figs 9C, 9G ).

Adult ( Figs 1A–1C , 10A ). General color of body, antennae, and wings black to dark brown ( Fig. 10A ). Length of each forewing: male 10–13 mm (mean = 11.9, n = 15), female 13–16 mm (mean = 15.1, n = 9). Antennae 1.5 times as long as forewings in male, 1.2 times in female. Head with pair of anteromesal, anterior, posterior and posterolateral setal warts; in dorsal view, each anteromesal wart round between antennal sockets, each anterior setal wart narrow, each posterior wart large oval, each posterolateral setal wart narrow and extending ventrad along posterior margin of eye. Venation as in Figures 1B, 1C : in each forewing, fork I rooted on discoidal cell about 1/3 its length in male, 1/ 8 in female; combined anal vein A1+2+3 with forewing coupling setae ventrally on false vein posterior of A1+2+3 (for fore- and hind wings to link on each side) ( Stocks 2010); in each hind wing, fork I rooted on discoidal cell about 1/3 its length in male, about 1/ 4 in female, crossvein m-cu present in male and female; costa with coupling setae dorsally to link with forewing.

Male genitalia ( Figs 1D–1I ). Tergum IX elongate, subtriangular to rectangular in dorsal view, bearing steep sides above basal setal warts ( Figs 1D, 1F ). In inferior appendages, each basal segment as long as preanal appendages, cylindrical with many long setae, slightly enlarged basoventrally in lateral view; each apical segment about 1/3 length of basal segment, apicomesal half with many brown teeth ( Figs 1E, 1F ). Preanal appendages elongate, broadest at basal half and tapered distally in lateral view, extending to posterior margins of lateral processes, each with several long setae near apex ( Figs 1D, 1F ). Median dorsal process of segment X with shallow apical concavity in dorsal view ( Fig. 1D ), and slightly clavate apically in lateral view ( Fig. 1F ). Pair of lateral processes of segment X protruding posteriorly, each with acuminate ventral projection extended posterad; each intermediate appendage very short, needle-like, directed anterolaterad ( Figs 1F, 1G ).

Phallus with phallotheca long, cylindrical; endotheca ventrally with pair of thick parameres ( Figs 1H, 1I ); aedeagus membranous with sclerotized ventral plate, phallotremal sclerite strongly curved dorsad, C-shaped in lateral view ( Fig. 1H ).

Female genitalia ( Figs 1J, 1K ). Sternum IX semicircular, as long as wide, with pair of dark pigmentations along median shallow sulcus in ventral view; each pigmentation subtriangular with acute apex directed posteromesad ( Fig. 1K ). Segment X with pair of fin-like dorsoposterior lobes, setose dorsally in dorsal view ( Fig. 1J ); with deep V-shaped incision in dorsal and ventral views ( Figs 1J, 1K ). Vaginal apparatus longer than sternum IX, anterior sclerite rectangular in ventral view ( Fig. 1K ).

Final instar larva ( Figs 9B–9D, 9G ). Length of final instar larva up to 17 mm. Head and thorax brown to reddish brown dorsally, with dark median longitudinal band from anterior margin of head to posterior margin of mesonotum ( Figs 9B, 9D ). Among primary setae on head, setae 9, 11, 14, 15, and 17 thick, brown; 16 fine, transparent; other setae fine, pale brown; 14 longest, 1.5 times as long as 15. Branched abdominal gills as in Fig. 9G present on each side of following segments (numbers of branches in parenthesis, n = 3): anterior dorsal gills on segments II (20–36), III (22–44), IV (22–34), V (28–29), VI (9–12), VII (9–10), and VIII (6–8); anterior ventral gills on segments II (29–46), III (28–56), IV (28–44), V (21–28), VI (13–24), VII (18–24), and VIII (7–12); anterior lateral gills on segments II (9–16) and III (7–10). Larval case cylindrical, slightly curved and tapered, constructed of coarse fragments of rock ( Fig. 9C ).

Specimens examined. Honshu, Aichi: 1 larva, Yato-cho, Seto-shi , 4.ix.1999, N. Kawase ; 2 larvae, Ichinoi, Maeguma, Nagakute-shi , 8.iv.2010, N. Kawase ; 2 males, same locality, 11.v.2011, H. Nishimoto . Mie: 6 males, 2 females, Washiyama, Kameyama-shi , 9.vi.2006, N. Kawase ; 1 male and 1 female, same locality, 17.vi.2006, H. Morita ; 1 larva, same locality, 29.ix.2006, N. Kawase . Shiga: 3 larvae, Kawashima, Adogawa-cho, Takashima-shi , 27.iv.2003, N. Kawase ; 8 males, 4 females, same locality, pupae collected on 24.v.2004, adults emerged on vi.2004, N. Kawase ; 1 larva, same locality, 30.ix.2007, N. Kawase ; 2 larvae, same locality, 3.xi.2010, N. Kawase ; 1 larva, Shichiri , Ryu-oh-cho, 20.v.2001 (no collector’s name is given) .

Distribution and habitat. Psilotreta japonica is an East Palearctic species sparsely distributed in central to western Honshu ( Fig. 11A ) and inhabits small water channels in lower hills or delta plains with spring water seeps ( Fig. 10E ).

Japanese name. Hitosuji-kiso-tobikera.

Figures

FIGURE 1. Psilotreta japonica (Banks 1906). 1A, male head and pro- and mesonota, dorsal; 1B, male right wings, dorsal; 1C, female right wings, dorsal; 1D–1I, male genitalia: 1D, dorsal; 1E, ventral; 1F, left lateral; 1G, variation of lateral process of segment X, left lateral; 1H, phallus, left lateral; 1I, same, ventral. 1J–1K, female genitalia: 1J, dorsal; 1K, ventral.Abbreviations: I, II, III, V = apical forks I, II, III, V; A1+2+3 = combined anal vein A1+A2+A3; aed. = aedeagus; amw. = anteromesal warts; aw. = anterior warts; bsw. = basal setal wart (paired); Cu1, Cu1a, Cu1b = cubital veins 1, 1a and 1b; dc = discoidal cell; end. = endotheca; fwcs on false vein = forewing coupling setae on false vein; hwcs on C = hind wing coupling setae on costa; inf.app. = inferior appendage (paired); int.app. = intermediate appendage (paired); lat.pr. = lateral process (paired); m-cu = cross vein between median and cubital veins; M1, M2, M3, M4 = median veins 1–4; mdp.tX = median dorsal process of tergum X; par. = paramere (paired); phall. = phallotheca; plw. = posterolateral warts; pr.app. = preanal appendage (paired); pw. = posterior warts; sIX = sternum IX; tIX = tergum IX; va. = vaginal apparatus; v.pr. = ventral projection (paired); X = segment X.

FIGURE 9. Larvae of Psilotreta spp. 9A, larvae and cases of P. voluta Kawase 2021. 9B–9C, P. japonica (Banks 1906): 9B, head and pro-, meso-, and metanota, dorsal; 9C, larva and case, left lateral. 9D–9F, head and pro-, meso-, and metanota, primary setae numbered: 9D, P. japonica; 9E, P. kisoensis Iwata 1928; 9F, P. spatulata sp. nov. 9G–9I, abdominal gill diagrams, left lateral: 9G, P. japonica; 9H, P. kisoensis; 9I, P. spatulata (sizes of dots represent the numbers of gill branches: large dots = 20 or greater; medium dots = 10–19; small dots = 1–9).

FIGURE 10. Psilotreta spp. and their habitats. 10A, P. japonica (Banks 1906), male, dorsal (the locality name in the label “Aoyagi Shin-Asahi” needs to be corrected to “Kawashima Adogawa”). 10B, P. voluta Kawase 2021, female habitus, left dorsolateral (photo by N. Shimura). 10C, mountain stream where adults of P. kisoensis Iwata 1928 and P. voluta were collected at light. 10D, small stream where many adults of P. kisoensis were collected by a Malaise trap. 10E, pools of a small lowland stream inhabited by larvae of P. japonica.

FIGURE 11. Distributions of Japanese Psilotreta species.