Psilotreta spatulata, Kawase, 2022

Kawase, Naoki, 2022, The genus Psilotreta Banks (Trichoptera, Odontoceridae) in Japan, Zootaxa 5195 (6), pp. 501-521 : 507-510

Psilotreta spatulata sp. nov.

( Figs 3A–3M, 9F, 9I, 11C)

Psilotreta sp. Tsuda 1938, 104, larva, case, Okinawa Island; Tanida 2003, 374, 380, case, Okinawa Island.

Diagnosis. The male genitalia of P. spatulata sp. nov. are most similar to those of P. moritai in the shapes of a pair of flattened spatula-shaped lateral processes but can be distinguished from the latter by the following structures: (1) the shape of each lateral process of tergum X is sub-triangular in lateral view in P. spatulata sp. nov. ( Figs 3I1–3I 4), but narrow rectangular in P. moritai ( Figs 4C 1, 4C 2); and (2) a pair of parameres in the phallus are long and located laterally in P. spatulata sp. nov. ( Figs 3J, 3K), but they are short and located ventrally in P. moritai ( Figs 4D, 4E).

Adult ( Figs 3A–3C). Body and antennae brown, wings light brown in alcohol. Length of each forewing: male 8.2–9.3 mm (mean = 8.7, n = 10), female 8.2–9.9 mm (mean = 9.3, n = 7). On head dorsally, eyes hemispherical, large especially in male ( Fig. 3A); locations and shapes of setal warts most similar to those of P. japonica ( Fig. 1A), but pair of anterior warts round oval (narrow transverse in P. japonica ). Venation similar to that of P. japonica ( Figs 1B, 1C), but crossvein m-cu absent in male hind wings ( Fig. 3B), and base of M3+4 and Cu1a directly connected without cross vein in female forewings ( Fig. 3C).

Male genitalia ( Figs 3D–3K). Tergum IX elongate, subtriangular in dorsal view, with steep sides above basal setal warts ( Figs 3D, 3E, 3H). Basal segment of each inferior appendage as long as preanal appendages, thick, slightly dilated at middle in lateral view, covered with setae; apical segment about 1/2 as long as basal segment, cylindrical with many small brown teeth on apical half ( Figs 3D, 3G, 3H). Preanal appendages elongate, compressed ( Fig. 3D). Median dorsal process of tergum X extending posteriorly, apical half clavate with truncate or round apex in dorsal view ( Figs 3D–3F 2). Pair of lateral processes of tergum X sclerotized, as long as median dorsal process, forming subtriangular plate in lateral view ( Fig. 3H); each with ventral projection extending antero-ventrad ( Figs 3I1–3I 4); posterior portion of each lateral process occasionally bearing few denticles ventrally (marked with arrows in Figs 3I 1, 3I 2), dorsal margins of lateral processes sometimes partially concave beside their intermediate appendages (marked with arrows in Figs 3E, 3I 4). Pair of intermediate appendages dark brown, heavily sclerotized, and strongly curved, C-shaped in lateral view, with acute apex directed posterad ( Figs 3D, 3H, 3I1–3I3), sometimes directed posterolaterad ( Figs 3E, 3I 4).

Phallus with phallotheca long, cylindrical; endotheca with pair of long, acute parameres laterally, each apex directed posterolaterad; aedeagus membranous with weakly sclerotized ventral plate, phallotremal sclerite V-shaped in ventral view, strongly curved dorsad ( Figs 3J, 3K).

Female genitalia ( Figs 3L–3M). Sternum IX semicircular to sub-triangular in ventral view with median longitudinal sulcus at posterior 2/3 of sternum IX between pair of indefinite broad pigmentations ( Fig. 3M). Posterior margin of segment X transverse, almost straight in ventral view; segment X with pair of flattened (depressed) dorsolateral lobes, sparsely setose ( Fig. 3L). Length of vaginal apparatus 2 times as long as sternum IX.

Final instar larva ( Figs 9F, 9I). Length up to 9 mm. Generally similar to those of P. japonica and P. kisoensis , but head and thoracic nota uniformly brown to dark brown without markings. Among primary setae on head, setae 9, 12, 14, and 15 thick, pale brown, other setae fine, white to near transparent; setae 14 longest and 1.5 to 2 times as long as 9; setae 9 second longest and about 1.5 to 2 times as long as 15. Branched gills as in Fig. 9I on each side of abdomen (numbers of branches in parenthesis, n = 3): anterior dorsal gills on segments II (8–10), III (8–14), IV (10), V (7–8), VI (4–7), VII (3–5) and VIII (0-4); anterior ventral gills on segments II (8), III (10–14), IV (8–12), V (8–11), VI (6–7), VII (4–7) and VIII (2–4); anterior lateral gills lacking. Case similar to that of P. japonica , but smaller.

Holotype. Male (in alcohol), Okinawa Island. Okuni-rindo, Iji, Kunigami-son , Okinawa Pref., 26°44'03" N 128°13'36"E, 21.iii.1999, T. Ito and A. Ohkawa ( LBM1410012539 ).

Paratypes. Okinawa Island : 9 males, 1 female, same data as holotype ( LBM1410012540 – LBM1410012549 ) ; 1 male, Sukuna-gawa, Yona, Kunigami-son , 26°45'N 128°13'E, 22.iii.1999, T. Ito and A. Ohkawa ( LBM1410012550 ) ; 4 males, same locality, 10.iv.2011, T. Ito ( LBM1410012551 – LBM1410012554 ) ; 9 males, 4 females, Genka, Nago-shi , 26°36'N 128°04'E, 8.iv.2011, T. Ito ( LBM1410012555 – LBM1410012567 ) ; 1 male, 5 females, Benoki, Kunigami-son , 26°8'N 128°3'E, 9.iv.1996, M. Aoyagi ( OMNH) ; 2 males, Hiji river, Kunigami-son , 26°7' N 128°2' E, 12.iv.1996, M. Aoyagi ( OMNH) ; 2 males, 1 female, Ryukyu University Station, Yona, Kunigami-son , 26°76'N 128°21'E, 11.iv.1996, M. Aoyagi ( OMNH) .

Other specimens examined. Okinawa Island: 1 male, 2 females, Genka, Nago-shi , 26°36'N 128°04'E, 8.iv.2011, T . Ito ; 3 males, same locality, 18.iii.2012, T . Ito ; 2 males, 2 females, Hogen-hashi, Genka, Nago-shi , 8.iv.2011, T . Ito ; 3 larvae, same locality, 22–24.xi.2010, T . Ito ; 6 larvae, same locality, 17–19.x.2014, T . Ito ; 1 female, Heigi-hashi, Genka, Nago-shi , 26°45'N 128°13'E, 18.iii.2012, T . Ito ; 1 larva, Teina-gawa, Nago-shi , 26°56'N 128°09'E, 10.i.1989, T . Kishimoto ( OMNH) ; 1 male, 1 female, Benoki, Kunigami-son , 26°8'N 128°3'E, 12.iv.1997, M. Yoshio ; 9 males, same locality, 12.iv.1997, T . Ueda ; 1 female, Ie-rindo, Sosu, Kunigami-son , 11–15.iv.2001, K. Uesugi ; 1 male, Hiji, Kunigami-son , 26°42' N 128°11' E, 27.iii.2006, K. Konishi ; 8 males, 2 females, same locality, 8.iv.2011, T . Ito ; 1 male, 1 female, same locality, 10.iv.2011, T . Ito ; 1 larva, same locality, 21.iii.1999, T . Ito and A. Ohkawa ; 1 male, Ryukyu University Station, Yona, Kunigami-son , 26°76'N 128°21'E, 2.iv.1986, N. Kobayashi ( OMNH) ; 1 male, same locality, 8.iv.1996, M. Aoyagi ; 2 larvae, Aha, Kunigami-son , 26°70'N 128°28'E, 16.x.1988, S. Shokita ( OMNH) ; 2 larvae, 4 cases, same locality, 5.ix.1994, M. Aoyagi ( OMNH) ; 1 male, Takasato, Ogimison , 26°41'N, 128°11'E, 17.iii.2012, T . Ito ; 1 larva and 2 pupae, Okukubi, Kin-cho , 26°28'20”N 127°55'35”E, 22.vi.2004 ; 3 males, 1 female, Okukubi, Kin-cho , 26°29'N 127°55'E, 1.iii.2011, R . Kuranishi. Ishigaki Island : 1 male, Omoto-dake, Ishigaki-shi , 18–19.iii.2002, I. Oshima, K. Sugishima and T . Yoshida .

Etymology. The Latin species epithet spatulata is derived from the spatula-shaped lateral processes in the male genitalia.

Distribution and habitat. Psilotreta spatulata sp. nov. is an Oriental species distributed in Okinawa and Ishigaki Islands in the Ryukyu Archipelago, southwestern Japan ( Fig. 11C) and was found in small mountainous streams.

Remarks. Tsuda (1938) recorded larvae and pupae of unidentified Psilotreta species from Okinawa Island and Tanida (1997) also recorded unidentified larvae and males from Okinawa Island. These larvae do not have distinct markings on their heads and thoracic nota as found in previously known Japanese species, P. japonica and P. kisoensis ( Tsuda 1938, Tanida 2003). The author examined the male and larval specimens deposited in Osaka Museum of Natural History that were used by Tanida (1997) and confirmed that both the adults and larvae agree with those of P. spatulata sp. nov. described above. Although the author could not examine specimens used by Tsuda (1938), they most probably belong to this species.

Japanese name. Okinawa-kiso-tobikera.