Macrostemum okinawanum ( Matsumura 1931 )

Ito, Tomiko & Nozaki, Takao, 2018, The family Hydropsychidae Curtis (Trichoptera) in the Ryukyu Archipelago, southwestern Japan, Zootaxa 4504 (4), pp. 545-565 : 563

Macrostemum okinawanum ( Matsumura 1931)

( Figs 9 L–9Y)

Macronema okinawanum Matsumura 1931, 1133 , male, Okinawa. Macrostemum okinawanum: Kuranishi and Kimura 2001 , 17–18, figs 1, 2, male, Amami-o-shima, Toku-no-shima, Okinawajima.

Specimens. Holotype male (pinned, cleared abdomen was dried up in a small vial), labeled “ Japan Matsumura, v.1907, Type Matsumura, Macronema okinawanum ”, Okinawa-jima (HU). Amami-o-shima: 10 males, Mt. Yuwan-dake, 300 m a.s.l., 19.vi.1998, K. Mizota, L; 1 male, 1 female, Sumiyo-cho, 24.vi.2007, M. Takai ( SCM); 2 females, Uken-son, 8.v.1998, H. Moriya; 1 male, Uken-son, 1.vii.2007, M. Takai ( SCM); 6 males, 1 female, Yuwan-gama, 18–19.iv.2015, SI, P; 1 male, Yamato-son, Yuwan-gawa, small stream, 18–19.iv.2015, SI, P; 2 males, Yuwan-gama, headwater, 18–19.iv.2015, SI, P; 2 males, Amami-shi, Naze-Asato, small stream, 20– 21.iv.2015, SI, P; 1 female, Amami-shi, Sumiyo-son, Yakugachi-gawa, 29.iv.2017, N. Katsuma. Okinawa-jima: 1 male, Kunigami-son, Okuma, 3.vi.2003, M. Tanaka ( MT); 1 male, 1 female, same locality, 24.ix, 2005, M. Tanaka ( MT).

Distribution. Japan: Ryukyu (Amami-o-shima, Toku-no-shima, Okinawa-jima). Endemic to central Ryukyu.

Remarks. This species was originally described from Okinawa-jima by Matsumura (1931), and Kuranishi and Kimura (2001) recorded from Amami-o-shima and Toku-no-shima for the first time. The holotype male deposited in Hokkaido University is in poor condition ( Fig. 9L ), but general appearance is similar to that of M. formosicolum . The dark markings on the right forewing are similar to that of the latter, but dark spots on cross veins, r and m-cu, are absent in the holotype of M. okinawanum ( Fig. 9M ). One male specimen collected from Okinawa-jima also has similar markings as the holotype ( Fig. 9P 1 ), but most dark spots of other specimens (1 male and 1 female) are indistinct or absent ( Fig. 9P 2 ). Kuranishi and Kimura (2001) reported that markings of forewings were variable in the Okinawa-jima population. On the other hand, specimens collected from Amami-o-shima have large and distinct markings, and the central three dark spots often fuse into a large arched band ( Kuranishi and Kimura 2001, fig. 2; Figs 9U 1 , 9U 2 ). These Amami-o-shima specimens also lack spots on cross veins r and m-cu.

We could not observe the holotype genitalia in detail because the abdomen in the small vial was dried and shrunk. However, morphology of two males collected from Okinawa-jima is very similar to that of M. formosicolum , although dorsal aspects of segment X are variable ( Figs 9R 1 , 9R 2 ). Male genitalia of specimens collected from Amami-o-shima are also similar to those of M. formosicolum ( Figs 9 V–9Y), but the apico-ventral lip of the phallotheca is slightly shorter than that of the latter ( Figs 9X, 9Y ).

Since populations of Okinawa-jima and Amami-o-shima may be a subspecies of M. formosicolum , further study with molecular data is needed to clarify the taxonomic status of this species. Macrostemum okinawanum has been listed in the Japanese Red List as a near-threatened species (Ministry of the Environment of Japan 2017).

Japanese name. Okinawa-hoshi-shima-tobikera.

Figures

FIGURE 1. Map of the Ryukyu Archipelago. Island names are shown for the islands with hydropsychid caddisfly records.

FIGURE 2. Diplectrona burha Schmid and D. albofaciata Ulmer. Diplectrona burha (2A–2I): male (2A–2F): 2A, abdominal segments V–X, left lateral; 2B, genitalia, left lateral; 2C, same, dorsal; 2D, left inferior appendage, ventral; 2E, phallic apparatus, left lateral; 2F, apex of phallic apparatus, ventral; female (2G–2I): 2G, abdominal segment VIII, left lateral; 2H, abdominal segments IX–X, left lateral; 2I, abdominal segments VIII–X, ventral. Diplectrona albofaciata (2J–2R): male (2J– 2O): 2J, abdominal segments IV–X, left lateral; 2K, genitalia, left lateral; 2L, same, dorsal; 2M, left inferior appendage, ventral; 2N, phallic apparatus, left lateral; 2O, apex of phallic apparatus, ventral; female (2P–2R): 2P, abdominal segment VIII, left lateral; 2Q, abdominal segments IX–X, left lateral; 2R, abdominal segments VIII–X, ventral. Abbreviations: V–X = abdominal segments V–X; l.l. = lateral lobe (paired); m.c.l. = mesocaudal lobe (paired); p.a. = preanal appendage (paired). Arrows, see text.

FIGURE 9. Macrostemum formosicolum (Matsumura) and M. okinawanum (Matsumura). Macrostemum formosicolum (9A– 9K): Holotype male from Taiwan (9A–9F): 9A, habitus, dorsal; 9B, left forewing, dorsal, venation and dark markings; 9C, genitalia, left lateral; 9D, same, dorsal; 9E, right inferior appendage, ventral; 9F, phallic apparatus, left lateral; specimens from Ishigaki-jima (9G–9K): 9G1, 9G2, right forewings, venation and dark markings (9G1, female; 9G2, male); 9H, male genitalia, left lateral; 9I, same, dorsal; 9J, phallic apparatus, left lateral; 9K, same, ventral. Macrostemum okinawanum (9L–9Y): Holotype male from Okinawa-jima (9L–9O): 9L, habitus, dorsal; 9M, right forewing, dorsal; 9N, genitalia, dorsal; 9O, right inferior appendage, ventral; specimens from Okinawa-jima (9P–9T): 9P1, 9P2, male right forewings, venation and dark markings; 9Q, male genitalia, left lateral; 9R1, 9R2, male genitalia, dorsal; 9S, phallic apparatus, left lateral; 9T, same, ventral; specimens from Amami-o-shima (9U–9Y): 9U1,9U2, male right wings, dorsal; 9V, male genitalia, lateral; 9W, same, dorsal; 9X, phallic apparatus, lateral; 9Y, same, ventral.