Arocatus elegantulus, Tsai & Rédei, 2017

Tsai, Jing-Fu & Rédei, Dávid, 2017, The genus Arocatus in Taiwan (Hemiptera: Heteroptera: Lygaeidae), Zootaxa 4299 (2), pp. 238-252 : 239-244

Arocatus elegantulus sp. nov.

( Figs. 1–18 , 23, 25 )

Caenocoris dimidiatus (non Breddin, 1907): Nakatani & Kohno (2012: 378). Misidentification.

Type material. HOLOTYPE: ♂, TAIWAN: Pingtung Co.: Sheding Park , 21°57'6.8"N 120°49'24.3"E, 23.v.2012, by hand , leg. W.N. Lu & Y.C. Lan; mounted on card, intact, deposited in NMNS ( Figs. 1–2 ). PARATYPES (12 ♂♂ 13 ♀♀): Hualien Co.: Hualien, 28.vi.2010 , leg. Y.B. Fan (1 ♀, dark variety, TFRI) ( Figs. 5–6 ); Pingtung Co.: Kenting National Park, Sheding , 21°57'34.1"N 120°49'21.2"E, 200 m, 23.xii.2012, beating , leg. Y.H. Peng (1 ♀ NMNS); Sheding Park , 21°57'6.8"N 120°49'24.3"E, 23.v.2012, by hand , leg. W.N. Lu & Y.C. Lan (1 ♂ NMNS); Sheding, Formosan sika deer sanctuary, 9.vi.2016, N 21°57'34.1"N 120°49'21.2"E , leg. Y.C. Lan (1 ♀, NMNS) ( Figs. 3–4 ); same locality, 14.vi.2010 , leg. C.S. Chiu & Y.C. Lan (1 ♂ HNHM); Kenting , 5–9.xii.1982, leg. S.C.

Lin & S.P. Huang (2 ♂♂ 2 ♀♀ TARI) ; Ouluanpi coast forest, 7–9.xii.1982, leg. S.C. Lin & S.P. Huang (1 ♀, TARI) ; Taitung Co.: Formosa, Koutousyo [= Lanyu Is.], xii.1931 – ii.1932, leg. S. Hirayama (4 ♂♂ 3 ♀♀ NTU); same locality and collector, iii–iv.1932 (1 ♀ NTU); Kotosho [= Lanyu Is.], 30.vii.1941, leg. T. Shiraki (1 ♀ NTU) . JAPAN: Kyushu : Cape Sata , 17.iv.1973, leg. Y. Furuki (1 ♀, dark variety, NSMT-I-He 1 1025); Ryukyu Archipelago : Okinawa Is., Hyakuna, 10.v.1973, leg. S. Hisamatsu (2 ♂♂, dark variety, NSMT-I-He 11023 and 11024); Taketomi-jima Is., 23.iv.1992, leg. S. Miyakawa (1 ♀, dark variety, NSMT-I-He 11027); Hateruma-jima Is., 17.iv.1993, leg. S. Miyakawa (2 ♂♂, dark variety, NSMT-I-He 1 1026 and 11028).

Additional specimens examined. JAPAN: Daito Islands : Daitozima (north) [= Kitadaitojima], 18.iii.1939, leg. M. Yanagihara (2 ♂♂ 1 ♀ NTU). These three specimens are in poor condition and therefore they are excluded from the type series.

Diagnosis. The new species differs from all known species of Arocatus in the combination of its nearly uniformly red head (except clypeus being more or less extensively black) and black pronotum broadly margined with red laterally. The external male genitalia are illustrated in Figs. 7–18 . A detailed comparison with its morphologically most similar congeners is given below under the Discussion of this species.

Description. Macropterous male and female ( Figs. 1–6 ). Colour. Head bright red, clypeus more or less extensively black (see Intraspecific variability); antenna and labium black. Pronotum black, broadly margined with red laterally and with a very narrow, almost linear median reddish vitta at about posterior third of posterior lobe; scutellum bright red with basal transverse impression and basal portions of lateral margins black, or completely black except extreme apex red (see Intraspecific variability); clavus and corium of fore wing black, base of costal margin bright red, membrane colourless; proepisternum and -meron black; hypomeron and most of epimeroid bright red; supracoxal lobes and a marginal fascia along posterior margin of epimeroid creamy white; ventral anterior collar creamy white or red; pterothoracic pleuron black; dorsal margin of meso- and metapleuron and posterior flange of metapleuron (metepimeron) bright red, peritreme and meso- and metathoracic supracoxal lobes creamy white; thoracic sternum black; legs blackish brown, with distal portion of coxae and whole tibiae creamy white; ground colour of abdomen bright red, with black suffusions or markings of different extension in both sexes (see Intraspecific variability).

Structure. Body elongate, parallel-sided, about 3.3–3.6 times longer than its greatest width. Body surface and vestiture. Body covered by a rather uniform, short, dense, adpressed, whitish pilosity, intermixed with scattered longer, semierect hairs ventrally; antenna with very short, dense, adpressed pilosity intermixed with a few sparsely distributed, semierect hairs distinctly shorter than diameter of their respective segments; femora and tibiae with relatively short, semierect, silvery pilosity intermixed with a few longer and more erect hairs especially on their dorsal and ventral surfaces. Head virtually unpunctured; callar lobe of pronotum finely, posterior lobe more strongly punctured, but punctures greatly concealed by the dense, adpressed pubescence; thoracic pleura apparently at most with shallow punctures, punctation not visible because of the dense, adpressed pubescence; abdomen unpunctured.

Head ( Fig. 23 ) 1.3–1.5 times as broad as long, about 1.7–1.85 (♂) / 1.45–1.70 (♀) times as broad as interocular distance; anteocular portion about as long as length of eye measured along body axis in lateral view; eyes relatively large; posterior margins of eyes and ocelli lie on a straight line; bucculae low, gradually tapering posteriad. Antenna ( Fig. 23 ) relatively long and gracile, about half as long as body; scape surpassing clypeus by its apical third; pedicel 0.8–0.9 times as long as width of head; basiflagellum about 8.3 times as long as its greatest width (close to apex), 0.7–0.8 times as long as width of head, 1.2–1.3 times as long as interocular distance; distiflagellum 1.20–1.25 (♂) / 1.25–1.3 (♀) times as long as pedicel. Labium reaching about base of abdominal venter III, segment I surpassing anterior margin of prosternum and reaching about posterior margin of ventral anterior collar. Prothorax. Pronotum ( Fig. 23 ) elongate subtrapezoid, about 1.6–1.8 times as broad as long; callar lobe about half as long as posterior lobe; anterior lobe with lateral margins gradually diverging posteriorly, broadest at its posterior margin; posterior lobe without any trace of elevated median carina, lateral margins nearly straight, gradually diverging. Pterothorax. Scutellum about 1.0–1.1 times as long as its basal width, about 1.9–2.3 times as long as claval commissure. Metathoracic scent gland ostiole and associated structures as in A. sericans .

Abdomen elongate oval, about as broad as fore wings in rest. External male genitalia ( Figs. 7–18 ). Genital capsule ( Figs. 7–8 ) rounded in posterior view, with dense, relatively short, semierect and erect pilosity; tergite IX ( Fig. 8 : t9) distinct, joining dorsal rim; dorsal sinus of posterior aperture ( Fig. 8 : dsi) vase-shaped, gradually broadened to about ventral one fourth, then sharply narrowed by a pair of hook-like protrusions; cuplike sclerite ( Figs. 7–8 : cs; Fig. 15 ) with a pair of robust suspensory apodeme ( Fig. 15 : sus), ventroposterior region fused with ventral rim of genital capsule thus forming a longitudinal ridge ( Fig. 15 : lrs). Paramere ( Figs. 9–14 ) with a hooklike, swollen crown and a basolateral tubercle. Phallus ( Figs. 16–18 ): basal plates joined with rigid support bridge complex consisting of a distinct transverse sclerotized region called ponticulus transversalis ( Dupuis 1970) (= support bridge of Yang & Chang 2000) ( Fig. 16 : pt), and an oblique tubular sclerotization called ductifer ( Bonhag & Wick 1953) (= supporting tube of Yang & Chang 2000) ( Figs. 17 : df) that receives ductus seminis ( Fig. 16 : ds) into the phallus; distal end of ductifer projects into a pair of transparent, elastic bands fused ventrally, the support bridge prolongations ( Fig. 16 : sbp), their distal ends connecting to the dorsal and ventral outgrowths of endophallic reservoir ( Fig. 18 ); phallosoma ( Fig. 16 : phs) subdivided into phallotheca and conjunctiva; phallotheca ( Fig. 16 : phth) barrel-shaped with a pair of subtriangular processes dorsally at its posterior margin; conjunctiva ( Fig. 16 : con) approximately of same length as phallotheca, tubular, without wrinkles or processes; aedeagus ( Fig. 17 : aed) (for terminology see Discussion) composed of a bellows-like basal vestibule ( Figs. 16–17 : bv), a helicoid complex ( Fig. 17 : hc) subdivided into a baseball-glove-like sclerotized part and a large membraneous lobe, and a penisfilum ( Fig. 17 : pfi) with two coils.

Measurements (n = 5 ♂♂ / 5 ♀♀) (in mm). Body length 6.86–8.33 / 7.74–9.70, length of head 1.03–1.18 / 1.23–1.32, width across eyes 1.42–1.71 / 1.57–1.91, interocular distance 0.88–1.02 / 1.08–1.18, lengths of scape: pedicel: basiflagellum: distiflagellum as 0.34–0.44: 1.18–1.47: 0.98–1.32: 1.08–1.86 / 0.44–0.49: 1.52–1.67: 1.32–1.42: 1.91–2.06, width of pronotum across apices of humeral processes 1.86–2.30 / 2.30–2.84, median length of scutellum 0.98–1.37 / 1.37–1.57, greatest width 2.00–2.30 / 2.20–2.84, greatest width of abdomen 1.71–2.30 / 2.25–2.74.

Intraspecific variability. The colour of the new species is significantly variable. Two distinct colour varieties could be recognized in the relatively small sample (15 ♂♂ 14 ♀♀) studied during the present study; they were identical in respect of the morphology of exoskeleton and male genitalia. They are informally called as “bright variety” and “dark variety” here (these names have no status for zoological nomenclature), and their diagnostic characters are summarized in Table 1. No intermediate specimens were seen. The bright colour variety occurs in the Hengchun Peninsula of the main island of Taiwan and in Lanyu (= Orchid) Island; only the dark variety was seen from the eastern part of the main island of Taiwan (Hualien) (only a single specimen examined) and from Kitadaitojima of Japan. Judging from the redescription of Nakatani & Kohno (2012) (as Caenocoris dimidiatus , misidentification), the population in the southern Ryukyus also belongs to the dark variety.

Bionomics. The species was recorded to feed on Parsonsia laevigata (Moon) Alston (Apocynaceae) by Nakatani & Kohno (2012) (as Caenocoris dimidiatus , misidentification). No host plant observation is available from Taiwan, but this plant also occurs in the country.

Distribution. Specimens were seen from Taiwan (Hengchun Peninsula and eastern part of the main island, Lanyu Island) and Daito Islands of Japan. At least part of, possibly all earlier records of Caenocoris dimidiatus Breddin, 1907 ( Azuma & Kinjo 1987, Miyamoto & Yasunaga 1989, Hayashi 2002, Nakatani & Kohno 2012, Ishikawa 2016) from Taiwan and various islands of the southern Ryukyus (Yonaguni Is., Iriomote Is., Ishigaki Is., Miyako Is., Okinawa Is., Kume Is.) pertain to this species.

Etymology. The specific epithet is the Latin adjective elegantulus , - a, - um, diminutive of elegans ‘elegant, handsome’, referring to the attractive appearance of the new species.

Discussion. Arocatus elegantulus sp. nov. strikingly differs from all congeners in its colour: the combination of the nearly uniformly red head (except variable black marking on clypeus), black pronotum with red lateral margins, nearly uniformly black clavus and corium (except red proximal portion of costal margin) and red abdominal venter (♂) with variable black suffusion (♀) is unique within the genus. Colour photos of representatives of all Indomalayan and Palaearctic species were presented by Gao et al. (2013); a comparison with them will render identification of the new species easy.

Within Arocatus the new species is most similar to members of the A. sericans species group (defined by Gao et al. 2013): A. sericans (Stål, 1859) , A. melanostoma Scott, 1874 , and A. pseudosericans Gao, Kondorosy & Bu, 2013 . Besides of the obvious differences in the colour of the head, pronotum, scutellum, and abdominal venter (cf. Gao et al. 2013), the new species differs from all the above three species in its vestiture: in all members of the A. sericans group the pilosity is distinctly longer, the dorsum of the head and the pronotum is covered by long, erect hairs ( Figs. 20–22 ), and the tibiae possess several erect hairs which are much longer than diameter of the tibia ( A. sericans : Fig. 22 ); in A. elegantulus sp. nov. the body is covered by short, adpressed pubescence, the head and the pronotum lack long, erect hairs ( Fig. 23 ), and the tibiae lack hairs conspicuously longer than their diameter ( Fig. 25 ). The new species and A. sericans differ from A. melanostoma and A. pseudosericans in their long antennae: their basiflagellum is about 1.2 times longer than the interocular distance, whilst it is distinctly shorter than the interocular distance in A. melanostoma , A. pseudosericans , and in most other congeners occurring in Asia.

Caenocoris dimidiatus Breddin, 1909 was recorded from various islands of the southern Ryukyus by different authors ( Azuma & Kinjo 1987, Miyamoto & Yasunaga 1989, Hayashi 2002, Nakatani & Kohno 2012). Following Gao et al. (2013) we recognize C. dimidiatus as a junior synonym of Arocatus sericans . The illustrations provided by Nakatani & Kohno (2012) leave no doubt that the species inhabiting the southern Ryukyus is A. elegantulus sp. nov. Caenocoris botoltobagensis , an unavailable name (nomen nudum) listed from Botol-Tobago (or Botel- Tobago, now Lanyu Island) without description by Esaki (1931) possibly also pertains to this species.

Figures

FIGURES 1 – 6. Arocatus elegantulus sp. nov., dorsal and ventral views Figs. 1 – 2, male holotype (“ bright variety ”, Taiwan: Pingtung County); Figs. 3 – 4, female paratype (“ bright variety ”, Taiwan: Pingtung County); Figs. 5 – 6, female paratype (“ dark variety ”, Taiwan: Hualien County). Scale in mm.

FIGURES 7 – 14. Arocatus elegantulus sp. nov., male genitalia. Fig. 7, genital capsule, posterior view (anal tube and left paramere removed, pilosity only shown on left side); Fig. 8, same, posterodorsal view (anal tube and parameres removed, pilosity omitted); Figs. 9 – 14, left paramere, six different aspects (pilosity omitted in Fig. 14). Lettering: cs = cuplike sclerite; dsi = dorsal sinus of posterior aperture; t 9 = tergite IX. Scales in mm.

FIGURES 15 – 19. External male genitalia of Arocatus elegantulus sp. nov. (Figs. 15 – 18) and A. nanus (Breddin, 1900) (Fig. 19). Fig. 15, cuplike sclerite, dorsal view; Fig. 16, phallus, dorsal view; Fig. 17, phallus, lateral view; Fig. 18, endophallic reservoir, ventral view; Fig. 19, phallus, lateral view. Lettering: aed = aedeagus; bv = basal vestibule of aedeagus; con = conjunctiva; df = ductifer; ds = ductus seminis; hc = helicoid complex; lrs = longitudinal ridge formed by fusion of ventroposterior region of cuplike sclerite with ventral rim of genital capsule; pfi = penisfilum; phs = phallosoma; phth = phallotheca; pt = ponticulus transversalis; sbp = support bridge prolongation; sus = suspensory apodeme. Scales in mm.

FIGURES 20 – 25. Diagnostic characters of Arocatus spp. Fig. 20, head, pronotum and right antenna of Arocatus pseudosericans Gao, Kondorosy & Bu, 2013 in dorsal view; Fig. 21, same, A. melanostoma Scott, 1874; Fig. 22, same, A. sericans (Stål, 1859); Fig. 23, same, A. elegantulus sp. nov.; Fig. 24, tibia and tarsus of right hind leg of A. sericans, posterior view; Fig. 25, same, A. elegantulus. In Figs. 20 – 23, pilosity shown only along the outline. Scales in mm.