Two new unique hibiscus-inhabiting species of the plant bug genus Sejanus Distant from Japan and Taiwan (Hemiptera: Heteroptera: Miridae: Phylinae) Author Yasunaga, Tomohide Research Associate, Division of Invertebrate Zoology, American Museum of Natural History, Central Park at 79 th Street, New York, NY 10024, c / o Nameshi 2 - 33 - 2, Nagasaki 852 - 8061, Japan. Author Duwal, Ram Keshari 0000-0002-2068-461X Visiting Researcher, Agriculture & Agri-Food Canada Environmental Health, K. W. Neatby: Bldg # 20, 960 Carling Avenue, Central Experimental Farm, Ottawa Ontario, Canada K 1 A 0 C 6. ramkeshariduwal @ gmail. com; https: // orcid. org / 0000 - 0002 - 2068 - 461 X ramkeshariduwal@gmail.com text Zootaxa 2022 2022-12-19 5222 2 155 167 journal article 53777 10.11646/zootaxa.5222.2.4 c60dc4ba-6d53-4a47-9460-80703bcfedce 1175-5326 7456681 55F69A43-2837-4E5F-936D-5ADD23BA5790 Checklist of Sejanus species known in Japan and Taiwan Tribe Leucophoropterini Schuh, 1974 Subtribe Leucophoropterina Schuh, 1974 Genus Sejanus Distant, 1910 S. amami Yasunaga, 2001 — Distribution : Japan (Amami-Oshima Is.)— Host : Unknown. S. azumanus Yasunaga & Duwal, 2020 — Japan (northern Honshu)— Elaeagnus umbellata Thunb. (Elaeagnaceae) . S. breviniger Yasunaga, 2001 — Japan ( Okinawa Is.).— Mallotus spp. (Euphorbiaceae) . S. epicurus Yasunaga & Duwal n. sp. — Taiwan ( Pingtung ).— Hibiscus taiwanensis S.Y. Hu (Malvaceae) . S. juglandis Yasunaga, 2001 — Japan ( Hokkaido , Honshu, Shikoku, Kyushu).— Juglans mandshurica Maxim. (Juglandaceae) . S. komabanus Yasunaga, Ishikawa & Ito, 2013 — Japan (Honshu), Korea (Chungcheongmam-do, Gyeonggi-do ).— Mallotus japonicus (Lf.) Müll.Arg. (Euphorbiaceae) . S. neofunereus Schuh, 1984 — Japan (Ryukyus: Okinawa Pref. ), Hong Kong , Philippines , Taiwan ( Nantou ).— Unknown. S. potanini (Reuter, 1906) — Japan ( Hokkaido , Honshu, Shikoku, Kyushu), Russian Far East, Korea , China .— Various deciduous broadleaf trees, particularly on willows, Salix spp. (Salicaceae) . S. ryujin Yasunaga & Duwal n. sp. — Japan (Kyushu: Nagasaki Pref. ). — Hibiscus hamabo Sieb. et Zucc. (Malvaceae) . S. vivaricolus Yasunaga & Ishikawa, 2013 — Japan (SW Honshu, Shikoku, Kyushu, and Nakadori, Wakamatsu and Yakushima Islands); Korea ( Gyeonggi-do , Jeju Island).— Elaeocarpus zollingeri K.Koch (Elaeocarpaceae) , Ligustrum japonicum Thunb. (Oleaceae) , Mallotus japonicus , Triadica sebifera (L.) Small, ( Euphorbiaceae ), Myrica rubra Sieb. & Zucc. (Myricaceae) , Zanthoxylum ailanthoides Sieb. & Zucc. (Rutaceae) ; this polyphagous species is considered predominantly predaceous. Taxonomy Genus Sejanus Distant Diagnosis: This genus was well defined by Schuh (1984) and Menard & Schuh (2014); distinguished from other genera of Leucophoropterini principally by the following characters: Body generally fuscous, small-sized (mostly 2–3 mm in total length); dorsum well-polished, shining, with uniformly distributed, simple setae; base of cuneus often with ivory (or occasionally orange-red) fascia (cf. Figs. 1H–J , 2F ) that is interrupted at middle or divided into two spots in some species ( Fig. 3I–J ); C- or J-shaped vesica (endosoma) with secondary gonopore opening at apex; small, thin-rimmed female sclerotized ring; and relatively simple interramal sclerite with comb-shaped microstructures and narrow posterior margin sclerite. Discussion. Sejanus Distant is a typical Indo-Pacific group and more than a few undescribed species are present mainly in the Oriental Region (Yasunaga & Duwal, unpublished data). For temperate and cold temperate climatic zones of Japan and adjacent regions, the fauna was considered to have been almost perfectly clarified by a series of recent works (e.g., Yasunaga, 2001a ; Yasunaga et al ., 2013 ; Oh et al ., 2020 ; Yasunaga & Duwal, 2021). Nonetheless, recent fieldworks have yielded two unique congeners that inhabit cryptic underside of hibiscus bracts and flower buds in southwestern Japan and Taiwan . FIGURE 1. Habitat (A–C) and habitus images of living individuals of Sejanus epicurus n. sp. (C–J) and Termatophylum orientale Poppius , female (K, sharing same niche). A–C. Hibiscus taiwanensis , breeding host of Sejanus epicurus n. sp. D. A male adult preyed upon by a spider. E–F. Fourth instar nymph. G. Final (5th) instar nymph. H. Adult female. I–J. Adult males. Several species of phyline plant bugs, e.g. Campylomma astica Yasunaga , C. hibiscicola Yasunaga , C. seunghwani Yasunaga and Decomioides verecundus Yasunaga , were documented to prefer similarly concealed habitats on Hibiscus tiliaceus L. (Yasunaga, 2021) or Macarang a spp. ( Euphorbiaceae ) ( Yasunaga, 2010 ; 2016 ). Within such niches, thrips ( Thysanoptera ), cicadellid leafhoppers(Auchenorrhyncha) and/or aphids (Sternorrhyncha) were observed to co-occur and are assumed to be prey of these phylines (e.g. Nakatani et al . 2017 ). Except for some Palearctic members (see above checklist), the breeding host plants of many Sejanus congeners are unknown (Menard & Schuh, 2014). In laboratory tests, both adult and immature forms of S. vivaricolus can be reared by brine-shrimp eggs (cf. Fig. 3F ); we consider that most Sejanus species are principally predaceous. Key to Sejanus species from Japan and Taiwan 1. Hemelytron totally shiny fuscous; base of cuneus with faint, narrow, and indistinct pale (reddish or whitish) fascia or spots if present at all (cf. Fig. 2E , 3C–E )......................................................................... 2 - Hemelytron almost entirely fuscous, except for base of cuneus with defined, white or ivory spots ( Fig. 3I–J ), or a continuous creamy white fascia ( Fig. 1H–J , 2F )...................................................................... 8 2. Apex of metafemur clearly yellow, yellowish brown or yellow-orange........................................... 3 - Metafemur entirely darkened, or its extreme apex only slightly pale............................................. 7 3. Antennal segment II pale brown with darkened apical 1/3–1/2 (♁)/ 1/4–1/6 ( ♀ ).................................... 4 - More than apical 2/3 (♁)/ 1/2 ( ♀ ) of antennal segment II darkened.............................................. 6 4. Male...................................................................................... S. azumanus - Female............................................................................................. 5 5. Labium as long as basal width of pronotum or metafemur; associated with Elaeagnus umbellata in northern Honshu................................................................................................. S. azumanus - Labium obviously longer than basal width of pronotum or metafemur; currently known to inhabit a halophyte, Hibiscus hamabo , in warm temperate climatic zone........................................................... S. ryujin n. sp. ( ♀ ) 6. Body larger; total body length more than 2.8 mm (♁)/ 2.7 mm ( ♀ ); length from apex of clypeus to cuneal fracture greater than 2.0 mm..................................................................................... S. potanini - Body smaller; total body length up to 2.6 mm (♁)/ 2.5 mm ( ♀ ); length from apex of clypeus to cuneal fracture less than 1.9 mm ...................................................................................... S. komabanus 7. Male antennal segment II shorter than basal width of pronotum; ventral cleft of scent efferent system elongate. S. vivaricolus - Male antennal segment II longer than basal width of pronotum; ventral cleft of scent efferent system rounded and shallow; currently known only from Okinawa Island........................................................ S. breviniger 8. All femora creamy yellow, not darkened ( Fig. 2I–J )............................................. S. epicurus n. sp. - All femora, at least their basal parts, dark brown to fuscous.................................................... 9 9. Apex of metafemur yellow or creamy white............................................................... 10 - Metafemur almost totally darkened...................................................................... 11 10. Body larger; total body length greater than 3.0 mm; base of cuneus usually with two ivory spots; specialist of a Japanese walnut, inhabiting deciduous forest zone................................................................. S. juglandis - Body tiny; total body length up to 2.5 mm ; base of cuneus with whitish brown fascia ( Fig. 2F ); inhabiting coastal Hibiscus hamabo ............................................................................... S. ryujin n. sp. (♁) 11. Antennal segment II longer than 0.88 mm (♁)/ 0.74 mm ( ♀ ); male antennal segment II wholly black; anterior ivory mark of cuneus usually continuous........................................................................ S. amami - Antennal segment II < 0.72 mm ; base of male antennal segment II pale; anterior ivory mark of cuneus usually divided into two spots or slightly interrupted medially ( Fig. 3I–J ).................................................. S. neofunereus