Sejanus ryujin, Yasunaga & Duwal, 2022

Yasunaga, Tomohide & Duwal, Ram Keshari, 2022, Two new unique hibiscus-inhabiting species of the plant bug genus Sejanus Distant from Japan and Taiwan (Hemiptera: Heteroptera: Miridae: Phylinae), Zootaxa 5222 (2), pp. 155-167 : 163

publication ID	https://doi.org/ 10.11646/zootaxa.5222.2.4
publication LSID	lsid:zoobank.org:pub:55F69A43-2837-4E5F-936D-5ADD23BA5790
DOI	https://doi.org/10.5281/zenodo.7456677
persistent identifier	https://treatment.plazi.org/id/03AB87FF-6B19-1755-819B-FF19FDA8F9CC
treatment provided by	Plazi
scientific name	Sejanus ryujin
status	sp. nov.

Treatment

Sejanus ryujin n. sp.

( Figs. 2A–H View FIGURE 2 ; 4E–G View FIGURE 4 ; 5H–O View FIGURE 5 ; 6G–L View FIGURE 6 ; 7E–H View FIGURE 7 )

Material examined. Holotype (♁). JAPAN: Kyushu, Nagasaki Pref., Omura City, Kushima , Ryujin Island , 32.895440, 129.953044, on Hibiscus hamabo Sieb. & Zucc. (flower bud or bract), 15 Jun 2022, T. Yasunaga ( AMNH) ( AMNH _ PBI 00380761 View Materials ) GoogleMaps . Paratypes: JAPAN: Same data as for holotype, 3♁ 8♀ ( TYCN) GoogleMaps .

Diagnosis. Recognized by its small size; darkened apical 1/3–1/2 (♁)/ 1/4–1/3 (♀) of antennal segment II; whitish brown anterior margin of male cuneus ( Fig. 2F View FIGURE 2 ); and creamy apex of each femur ( Fig. 2G–H View FIGURE 2 ). Externally most similar to S. komabanus , from which the present new species can be distinguished by the characters suggested in above key, in addition to the whitish brown anterior margin of cuneus in male ( Fig. 2F View FIGURE 2 ), curved ( Fig. 6I View FIGURE 6 , vs. 6M), and narrower apical part of vesica ( Fig. 4H View FIGURE 4 , vs. 4J). Sejanus komabanus is known to propagate on Mallotus japonicus and the distribution is restricted to central Honshu ( Yasunaga et al., 2013).

Description. Male: Macropterous. Body elongate oval, subparallel-sided, small; dorsal surface shiny fuscous, well-polished, with uniformly distributed, pale, simple, semierect setae, lacking additional vestiture ( Fig. 5J View FIGURE 5 ). Head somewhat rounded anteriorly; vertex weakly carinate basally ( Fig. 5J–K View FIGURE 5 ). Antenna creamy yellow, rather short; segment I about as thick as II; apical 1/3–1/2 of segment II dark reddish brown. Labium shiny reddish brown, reaching apex of metacoxa; apical half of segment IV darkened. Pronotum polished, minutely punctate; scutellum flat; pleura dark brown, with sparsely distributed, simple, reclining setae ( Fig. 5I View FIGURE 5 ); metathoracic scent efferent system grayish brown, with rounded orifice and ear-like peritreme ( Fig. 5L View FIGURE 5 ). Hemelytron shining, uniformly fuscous; basal 1/4 of cuneus whitish brown; membrane including veins pale smoky brown. All coxae and femora shiny chocolate brown; apex of each femur and all tibiae creamy yellow; tibial spines pale brown; apex of each tibia and tarsomere III slightly darkened; meta-tarsomere II slightly longer than III ( Fig. 5M View FIGURE 5 ); pretarsal structure as in Fig. 5N View FIGURE 5 ; parempodia setiform, relatively long. Abdomen shiny dark brown, partly tinged with red. Male genitalia ( Figs. 4E View FIGURE 4 ; 6G–L View FIGURE 6 ): Phallotheca sharply tapered and weakly curved towards apex ( Fig. 6I View FIGURE 6 ); left paramere with rather long hypophysis ( Fig. 6G–H View FIGURE 6 ); right paramere small, with reduced hypophysis ( Figs. 6H View FIGURE 6 ); endosoma (vesica) Cshaped ( Fig. 6K View FIGURE 6 ), with slightly widened and spinulate apical part ( Fig. 6J View FIGURE 6 ).

Female: Body ovoid, shorter than male; dorsum totally shiny fuscous, without pale macula or spot ( Fig. 2E View FIGURE 2 ). Antennal segment II slenderer and shorter, with apical 1/4–1/3 darkened. Pretarsal structure as in Fig. 5O View FIGURE 5 Female genitalia ( Figs. 4F–G View FIGURE 4 ; 7E–H View FIGURE 7 ): Sclerotized ring relatively small, suboval ( Figs. 4F View FIGURE 4 , 7E View FIGURE 7 ); interramal sclerite with roughly arranged and rather sparsely distributed scaly microstructures ( Fig. 7G View FIGURE 7 ).

Measurements: See Table 1 View TABLE 1 .

Etymology. Named for the type locality, Ryujin Island (Ryujin means the Dragon-God traditionally worshiped as a protectorate god of the sea, water, wealth and/or fortune); a noun in apposition.

Distribution. Japan (Kyushu: Nagasaki Pref.).

Biology. The breeding host was confirmed as Hibiscus hamabo ( Fig. 2A–C View FIGURE 2 ), a semi-mangrove halophyte grown along restricted coasts in southern Japan. The immature forms are yet to be found but newly emerged adults were collected in mid-June. As subsequent field investigation in September and October could not yield additional material and the host trees are defoliated during winter, this new species is currently assumed to be univoltine.

Sejanus ryujin n. sp. was observed to share the niche (hibiscus bract and flower bud) with two predaceous bugs, Campylomma lividum Reuter ( Phylinae : Nasocorini) and a minute pirate bug, Orius strigicollis (Poppius) ( Anthocoridae : Oriini ) as well as an undetermined thrips ( Thysanoptera : Phlaeothripidae ) ( Fig. 2K View FIGURE 2 ). This new mirid species also appears to pray on the thrips.