Single Taxon Treatment New record of the pentatomine stink bug species Caystrus orientalis Zhang and Lin ( Hemiptera : Pentatomidae ) from Japan

Corresponding author: Tadashi Ishikawa (chuishikawa@gmail.com) Academic editor: Laurence Livermore Received: 13 Feb 2018 | Accepted: 18 Apr 2018 | Published: 24 Apr 2018 Citation: Tachi H, Ishikawa T (2018) New record of the pentatomine stink bug species Caystrus orientalis Zhang and Lin (Hemiptera: Pentatomidae) from Japan. Biodiversity Data Journal 6: e24439. https://doi.org/10.3897/BDJ.6.e24439


Introduction
The stink bug species Caystrus orientalis Zhang and Lin, 1985, belonging to the pentatomine tribe Caystrini, was described based on one female in Fujian Province, China (Zhang and Lin 1985).Subsequently, Lin and Zhang (1993) and Lin et al. (1999) recorded it from Jiangxi and Yunnan Provinces, China.To date, the species has been known to occur in south-western and south-eastern China.
In Japan, two species of the genus Caystrus Stål, C. depressus (Ellenrieder, 1862) and C. obscurus (Distant, 1901), have been recorded by Takara (1957) and Ishikawa et al. (2012), respectively.However, the existence of an additional species of this genus or an allied genus has been suggested under indeterminate conditions, such as Caystrus sp.(Nozaki et al. 2016) and Neodius sp.(Nagasaki Prefecture 2001); Neodius Bergroth is currently regarded as a synonym of Caystrus (Rider 2006).Our recent closer examination of the undetermined species unequivocally verified its identity as C. orientalis.
The present paper reports Caystrus orientalis as the third representative of Caystrus in Japan, providing diagnostic morphological characters with photographic images to aid in accurate identification; the habit and habitat preference are also briefly discussed.

Materials and methods
Dried specimens were used.Morphological observations, including those of genital structures, were made under Olympus SZ60 and SZX16 binocular microscopes.Digital images of the specimens were captured using a Nikon D200 digital camera body and Nikon AF Micro-Nikkor 60 mm f/2.8D lens and using a KEYENCE digital microscope system (VHX-1000 digital microscope, VHX-S50 observation system, VHX-1100 multi-scan camera and VH-Z20R zoom lens).The terminology used herein generally follows that of Tsai et al. (2011).The specimens examined in this study are preserved in the Laboratory of Entomology, Faculty of Agriculture, Tokyo University of Agriculture, Japan, except for three specimens collected from Nagasaki Prefecture, which will be housed in Nagasaki North High School, Science Club, Nagasaki City, Japan.

Diagnosis
Caystrus orientalis can be distinguished by a combination of the following characters: body 11.9-14.1 mm long (average 13.5 mm); body generally dark brown to blackish (Fig. 1); each mandibular plate not contiguous to another in front of clypeus (Fig. 1a, c); antennae brown to dark brown, with basal half of segment V pale (Fig. 1); mesal longitudinal stripe on pronotum and scutellum entirely unclear, often interrupted with blackish punctures (Fig. 1a, c); legs generally dark yellow to dark brown (Fig. 1b, d); venter of abdomen blackish, with connexivum yellowish to dark yellow, excluding blackish punctures (Fig. 1b, d); ventral rim of genital capsule (pygophore) medially notched in M-shape (Fig. 2a, b); M-shaped notch one-fifth as wide as genital capsule (Fig. 2b); apex of paramere triangular in caudal view, with dorsal lobe tapering and acute at apex and ventral lobe rounded at apex (Fig. 2c, d); apical receptacle of spermatheca provided with 2 processes, one directed upward or laterad, other directed downward (Fig. 2e).

Discussion
As mentioned above, two species of the genus Caystrus, C. depressus (Ellenrieder, 1862) and C. obscurus (Distant, 1901), were previously reported in Japan (Takara 1957, Ishikawa et al. 2012, Ishikawa 2016).Amongst the Japanese congeners, C. orientalis is separable from the other two species by a combination of the following characteristics: relatively large body, generally dark brown to blackish in colour; blackish abdomen venter, with a yellowish to dark yellow connexivum; ventral rim of the genital capsule with a medial M-shaped notch, which is one-fifth as wide as the genital capsule; triangular crown of paramere in caudal view, with the dorsal and ventral lobes acute and rounded at the apex, respectively; and apical receptacle of spermatheca with an upwardly or laterally directed process and a downwardly directed process.
According to Nozaki et al. (2016), the adults and nymphs of Caystrus orientalis inhabit (or often coexist with) the stems or soft litter layers of the base of Miscanthus floridulus (Labill.)Warb.(Poaceae) bushes in Kumamoto Prefecture, Kyushu, Japan.Similarly, we collected the Ryukyuan individuals of C. orientalis from the lower parts of M. sinensis Anderss bundles (Fig. 3).Therefore, this species appears to feed on Miscanthus grasses.Additionally, we found that the species was occasionally attracted to UV light at night, as reported in Nagasaki Prefecture (2001).Habitat of Caystrus orientalis on Ishigaki Island, the Ryukyu Islands, Japan.
New record of the pentatomine stink bug species Caystrus orientalis Zhang ...