Rhysida immarginata (Porat, 1876)

Figs 1, 6, 7

Rhysida immarginata Pocock, 1891 - Kraepelin 1903: 143; Lewis 2001: 45; Siriwut et al. 2018: 1022, figs 9–11.

Rhysida nuda immarginata Attems, 1930: 190.

Rhysida nuda Attems, 1930: 189, figs 236–237; Attems 1938: 337; Tran et al. 2013: 227.

Examined materials.

Vietnam • 1 specimen; Ha Giang Province, Tay Con Linh NR, natural forest; 22.78121°N, 104.85867°E; 1,113 m a. s. l.; 2019; col. A. D. Nguyen leg; HG.TCL.02 . • 3 specimens; Dien Bien Province, Muong Nhe Natural Reserve; residential area, 21.21278°N, 103.39833°E; 610 m a. s. l.; May 2018; S. X. Le & H. D. Nguyen leg.; DB 019, DB 013, DB 018 ; • 2 specimens; same location, residential area; 22.30056°N, 102.39833°E; 558 m a. s. l.; Nov. 2017; S. X. Le leg.; MN 018.1, MN 106 . • 1 specimen; Son La Province, Ta Xua NR, residential area, 21.35972°N, 104.66972°E; 673 m a. s. l.; 11 Oct. 2017; S. X. Le and H. T. Vu leg.; HNUE.TX.D4.001 • 1 specimen; same location, bamboo forest; 21.33833°N, 104.69139°E; 429 m a. s. l.; 14 Oct. 2017; L. K. Ha leg.; HNUE.TX.142 . • 2 specimens; Hoa Binh Province, Thuong Tien NR, residential area; 20.66127°N, 105.46142°E; 175 m a. s. l., Jul. 2020; H. D. Nguyen leg.; HNUE.TT.202 to 203 . • 4 specimens; Phu Tho Province, Xuan Son NP, natural forest; 21.11426°N, 104.95845°E; 511 m a. s. l.; 13 Jun. 2014; S. X. Le leg.; VRTC.XS.015 to 016, VRTC.XS.018 to 019 • 4 specimens; same location, natural forest; 21.118219°N, 104.95159°E; 492 m a. s. l.; 10 Jun. 2014; S. X. Le leg.; VRTC.XS.006, VRTC.XS.009 to 010, VRTC.XS.021 • 4 specimens; same location, mixed wood – bamboo; 21.136413°N, 104.95244°E; 524 m a. s. l.; 12 Jun. 2014; S. X. Le leg.; VRTC.XS.011 to 014 • 1 specimen; Xuan Son NP, natural forest; 21.12622°N, 104.92145°E; 556 m a. s. l.; 14 Jun. 2014, S. X. Le leg.; VRTC.XS.025 . • 1 specimen; Vinh Phuc Province, Tam Dao NP, residential area; 21.45627°N, 105.64222°E; 1.001 m a. s. l.; Oct. 2022; A. D. Nguyen leg.; IEBR.VP.132 . • 1 specimen; Hai Phong city, Duong Kinh, residential area; 20.82540°N, 106.68219°E; 5 m a. s. l.; 16 May 2021; S. X. Le leg.; VRTC.HP.01 . • 8 specimens; Thai Binh Province, Tien Hai NR, coniferous forest; 20.25306°N, 106.59306°E; 8 m a. s. l.; 2021; H. D. Nguyen leg.; HNUE CHI 1066 to 1067, HNUE CHI 1081, HNUE CHI 1088, HNUE CHI 1092, HNUE CHI 1096, HNUE CHI 1098, HNUE CHI 1100 . • 1 specimen; Ha Noi city, Ba Vi NP, natural forest; 21.08191°N, 105.35786°E; 487 m a. s. l.; Aug. 2016; S. X. Le leg.; VRTC.BV.104 • 5 specimens; same location, residential area; 21.04000°N, 105.13389°E; 13 m a. s. l.; 8 Jan. 2019; H. D. Nguyen leg.; VRTC.HN.004 to 008 • 1 specimen; same location, Cau Giay district, residential area; 21.04673°N, 105.80093°E; 9 m a. s. l.; 10 Sep. 2018; H. T. Vu leg.; IEBR.SP.01 . • 4 specimens; same location, Ha Dong district, residential area; 20.946386°N, 105.78258°E; 8 m a. s. l.; 5 Dec. 2021; S. X. Le leg.; VRTC.KH.001 to 004 • 1 specimen; same location, Thanh Xuan district, residential area; 20.99984°N, 105.81969°E; 9 m a. s. l.; 6 Jun. 2021; A. D. Nguyen leg.; VRTC.TX.001 • 7 specimens; same location, Tay Ho district, agricultural area; 21.075970°N, 105.83600°E; 12 m a. s. l.; 12 Jan. 2022; S. X. Le and T. T. Do leg.; VRTC.HN.003, VRTC.HN.005 to 008, VRTC.HN.015, VRTC.HN.020 • 1 specimen; same location, Cau Giay district, residential area; 21.069060°N, 105.79577°E; 15 m a. s. l.; May 2023, D. X. Le leg.; VRTC.HN.021 . • 1 specimen; Nghe An Province, Pu Mat NP, natural forest; 18.93889°N, 105.23344°E; 437 m a. s. l.; 17 Apr. 2018; S. X. Le leg.; VRTC.PM.033 • 1 specimen; same location, Pu Mat NP, natural forest; 18.95917°N, 104.18347°E; 254 m a. s. l.; 23 Apr. 2018; S. X. Le leg.; VRTC.PM.034 . • 4 specimens; Dong Thap Province, Tram Chim NP, natural forest, 10.71746°N, 105.52186°E, 7 m a. s. l., 6 Oct. 2018, D. H. Lam leg.; VRTC.TrC.007 to 009, VRTC.TrC.011 • 1 specimen; same location, Tram Chim NP, natural forest; 10.69942°N, 105.52884°E; 11 m a. s. l.; 18 Mar. 2023; S. X. Le and H. D. Nguyen leg.; VRTC. TrC 012 • 1 specimen; same location, Tram Chim NP, natural forest; 10.71075°N, 105.53567°E; 7 m a. s. l.; 20 Mar. 2023; S. X. Le and H. D. Nguyen leg.; VRTC.TrC 033 .

Diagnosis.

Body with 21 leg-bearing segments. LBS 7 th with spiracles. Antennae (Fig. 6 A) composed of 18–20 articles, of which three basal ones glabrous dorsally. Cephalic plate without lateral and posterior marginations; posterior edge straight, and covered by tergite 1 (Fig. 6 A). Tooth-plates with 4 (5) + 4 (5) teeth prominently; trochanteroprefemora of forcipular strong, with 3 + 4 prominent teeth (one apical and two-three lateral teeth)); coxosternite with short median suture starting from toothplate (Fig. 6 C). Tergites (Figs 6 B, 7 C) without punctate and short median sulcus; lateral margination absent (except for tergite 21, complete); tergites 6–20 with complete paramedian sutures and incomplete on tergites 3–5. Sternites 2–19 with incomplete (only 10–15 % length of sternites) paramedian sutures on anterior and posterior parts (Fig. 6 D). Coxopleural process with 1 (2) apical and 1 (2) subapical spine, lateral and dorsal spines absent (Fig. 7 B). Leg 1 with 1 fermoral, 1 tibial, and 2 tarsal spur (s) (Fig. 7 A). Ultimate leg (Fig. 7 D) prefemora with 1–2 VL, 0–1 VM, 0–1 M, and 0–2 DM spines.

Remarks.

R. immarginata is clearly distinguished from other Rhysida species in Vietnam by the absence of lateral tergite margination, except for tergite 21. This is also the characteristic supporting the division of Rhysida species into two main groups, the longipes group and the immarginata group, as mentioned in the study of Joshi et al. (2019).

Our examined specimens were consistent with the description in Siriwut et al. (2018) in most characteristics. However, the descriptions by Siriwut et al. (2018) do not mention the presence of a median suture on the coxosternite, which we observed to be present, albeit very briefly (Fig. 6 C).

Additionally, the length of the antennae reaches the boundary between tergites 5 and 6, which aligns with Siriwut et al. (2018) and is confirmed by Schileyko and Stoev (2016). This differs from Attems (1930) and Waldock and Lewis (2014), where the antennae are shorter, reaching only the posterior margin of tergite 3, and even shorter in Koch (1985).

Distribution.

This species occurs in Africa (Congo, Sudan), South America (Bolivia, Cuba, El Salvador, Guatemala, Peru, Venezuela, and Uruguay), and South and Southeast Asia (Taiwan, Cambodia, Indonesia, Kalimantan, Maluku, Myanmar, the Philippines, Singapore, Sri Lanka, Sumatera, Papua New Guinea, Malaysia, India, Nepal, Thailand, and Laos) (Bonato et al. 2016; Schileyko and Stoev 2016; Siriwut et al. 2018).

In Vietnam it was recorded in Quang Ninh Province (Ha Long Archipelago) and Nghe An Province (Vinh city) by Attems (1938), and Ha Giang, Dien Bien, Son La, Hoa Binh, Phu Tho, Vinh Phuc, Hai Phong, Thai Binh, Ha Noi, and Dong Thap in this study. The distribution of R. immarginata was further updated (Fig. 1).