﻿Taxonomic review of Amemboa Esaki, 1925 from China, with description of a new species (Hemiptera, Heteroptera, Gerridae)

﻿Abstract The species of Amemboa Esaki, 1925 from China are reviewed. Amemboahainanicasp. nov., is described from Hainan Island, and Amemboaburmensis J. Polhemus & Andersen, 1984 is newly recorded from China. Additionally, diagnoses and new distribution records are provided for six species previously reported from China: A.brevifasciata Miyamoto, 1967, A.cristata J. Polhemus & Andersen, 1984, A.esakii J. Polhemus & Andersen, 1984, A.fumi Esaki, 1925, A.riparia J. Polhemus & Andersen, 1984, and A.speciosa J. Polhemus & Andersen, 1984. Photographs and line drawings of the habitus, the diagnostic characteristics of males, in-situ habitus, and their habitats are presented. A key and a distribution map are also provided for species of Amemboa occurring in China.


Introduction
Amemboa Esaki, 1925 belongs to the water strider subfamily Eotrechinae.Members of this genus typically inhabit the edges of slow-flowing rivers or still ponds near rivers.The species of Amemboa are found in South and Southeast Asia, ranging from India to the Philippines, and exhibit a notable diversity in tropical regions (Polhemus and Andersen 1984;Zettel 1995Zettel , 1998Zettel , 2002;;Zettel andChen 1996, 1997;Zettel et al. 2007;Polhemus and Tran 2012;Basu et al. 2014;Polhemus 2017;Jehamalar et al. 2023).Jehamalar et al. (2023) classified Amemboa into 11 species groups based on the morphological characteristics of males.Prior to this study, Amemboa comprised a total of 28 described species (Jehamalar et al. 2023).
Six Amemboa species were recorded from China: Polhemus and Andersen (1984) described two species from Taiwan Island, namely A. esakii J. Polhemus & Andersen, 1984and A. fumi Esaki, 1925. Cheng et al. (2006) reported the distribution of "A.lyra (Paiva, 1918)" in Yunnan.However, Zettel et al. (2007) re-examined the specimens of Cheng et al. (2006) and found that the profemora of males correspond to A. riparia J. Polhemus & Andersen, 1984.Amemboa riparia was recognized as a synonym of A. lyra by Zettel and Chen (1996) and subsequently re-established as a valid species by Polhemus and Tran (2012).Therefore, the species
Comparative notes.Amemboa hainanica sp.nov. is most similar to A. cambodiana D. Polhemus, 2017.In males of both species, the lateral arm of the proctiger in lateral view exhibits a distinct subapical notch on its dorsal margin, isolating a small, slightly recurved apical process, which gives the lateral arm a hooked appearance (Fig. 10A; also see Polhemus 2017: fig.22).These are the only two known Amemboa species that share this morphological characteristic.Besides, the ventral side of the profemur bears two tufts of dark setae in the males of both species (Fig. 6A; also see Polhemus 2017: fig.19).Some color patterns of both species are also similar (Figs 2A, 12A; also see Polhemus 2017: figs 14, 15).However, these two species can be distinguished by the following characteristics.The apical hook of lateral arm is more acutely pointed in A. cambodiana (see Polhemus 2017: fig.22), while it is blunter in A. hainanica sp.nov.(Fig. 10A).The subapical process is weakly developed in A. cambodiana, while it is more distinct in A. hainanica sp.nov.(Fig. 10A; also see Polhemus 2017: fig.22).The two species can also be separated by the shape of their pygophores, which is campanulate in A. cambodiana (see Polhemus 2017: fig.21) and lacks the pair of lateral blunt processes seen in A. hainanica sp.nov.(Fig. 9A).
Etymology.The specific epithet hainanica refers to the island of Hainan, China, the only area in which this species has so far been collected.
Remarks.This species was previously recorded in Hainan (Zettel et al. 2007), but we have not found it in this distribution.Comparative notes.Amemboa burmensis is most similar to A. kumari (Distant, 1910) and A. cambodiana D. Polhemus, 2017, see comparative notes in Polhemus and Andersen (1984) and Polhemus (2017).

New record for China
Distribution.China: Yunnan (Fig. 18).Myanmar: Shigbwiyang (Polhemus and Andersen 1984).Figure 16.Amemboa hainanica sp.nov., live habitus in situ A an apterous male moving on the water surface B an apterous male cleaning its forelegs C an apterous male and a nymph standing on the water surface (photographed by Fan Gao).Images not to scale.
Habitat.We found A. burmensis inhabiting stagnant pools at the edges of a wide river (Fig. 15B), located near the lower altitudes of the forest in Tong-biguan, Yunnan.
Remarks.In the original description of A. burmensis, Polhemus and Andersen (1984) described the profemur of males as follows: "Fore femur moderately incrassate in basal 1/2 (fig.36), with an elongate patch of short dark hairs on ventral side".However, among the specimens collected from China, this elongate tuft of setae is either more distinct than the original description (Fig. 6C) or nearly absent (Fig. 6D).We speculate that this may be caused by wear of the setae, or there may be two phenotypes of this species.Diagnosis.Color pattern as shown in Figs 2E, 3D, 12E.Males: profemur moderately incrassate (Fig. 6E); ventral side of the profemur with one elongate crest of dark setae on apical 1/2 and an additional elongate crest of dark setae on basal 1/2 (Fig. 6E); protibia slightly curved and with a tumescence on basal 1/3 (Fig. 6E); abdominal segment VIII relatively long (Fig. 7D); pygophore posteriorly with a bifid median process and a pair of strongly produced lateral processes in ventral view (Figs 8D, 9D); median process of pygophore relatively narrow in lateral view (Figs 10D, 11D); lateral arm of proctiger relatively curved and slender in ventral view (Fig. 8D), without subapical process in lateral view (Fig. 10D)
Comparative notes.Amemboa esakii is distinct from all congeners in having a T-shaped median process and a truncate posterior margin of pygophore in ventral view (Figs 8E,9E).
Distribution.China: Taiwan (Fig. 18).6G); ventral side of the profemur with two tufts of dark setae on the apical 1/2 (Fig. 6G); protibia slightly curved and with an indistinct tumescence on basal 1/3 (Fig. 6G); abdominal segment VIII relatively short (Fig. 7F); pygophore posteriorly with a digitate median process in ventral view, also with a pair of blunt processes at lateral sides of the median process, without distinct angular lateral process (Figs 8F, 9F); median process of pygophore relatively narrow in lateral view (Figs 10F, 11F); lateral arm of proctiger relatively curved and slender in ventral view (Fig. 8F), without subapical process in lateral view (Fig. 10F).

Figure 5 .
Figure5.Morphological features of Amemboa hainanica sp.nov.A body of male, dorsal view B body of male, ventral view C body of male, lateral view D body of female, dorsal view E body of female, ventral view F body of female, lateral view G left foreleg of male, dorsal view H pygophore and proctiger of male, ventral view I pygophore of male, ventral view J pygophore and proctiger of male, lateral view K pygophore of male, lateral view.Scale bars: 1 mm (A-F); 0.2 mm (G); 0.1 mm (H-K).

Figure 15 .
Figure 15.Habitat of Amemboa spp.A habitat of A. hainanica sp.nov., a tranquil pool at the base of the waterfall B habitat of A. burmensis J. Polhemus & Andersen, 1984, a wide, rocky river C habitat of A. riparia J. Polhemus & Andersen, 1984, a muddy pool beside the river D habitat of A. riparia, a small stream in the jungle.

Figure 17 .
Figure 17.Amemboa riparia J. Polhemus & Andersen, 1984, habitat and live habitus in situ A habitat of A. riparia, at the banks of a still pond next to the ravine rainforest B apterous male, dorsal view C apterous female, lateral view.Images not to scale.