Macrostemum okinawanum
Creators: name: Ito, Tomiko
name: Nozaki, Takao
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Trichoptera
Hydropsychidae
Macrostemum
Macrostemum okinawanum

description: 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.
description: Published as part of Ito, Tomiko & Nozaki, Takao, 2018, The family Hydropsychidae Curtis (Trichoptera) in the Ryukyu Archipelago, southwestern Japan, pp. 545-565 in Zootaxa 4504 (4) on page 563, DOI: 10.11646/zootaxa.4504.4.6, http://zenodo.org/record/2606666