Fossia bachma hainanensis, Huang & Volynkin & Zhu & Wang & Huang, 2021

Huang, Chu-Yang, Volynkin, Anton V., Zhu, Li-Juan, Wang, Min & Huang, Si-Yao, 2021, Contribution to the knowledge of the genus Fossia Volynkin, Ivanova & S. - Y Huang, 2019 (Lepidoptera: Erebidae: Arctiinae: Lithosiini) from China with description of a new subspecies, Zootaxa 5023 (2), pp. 284-292 : 286-287

Fossia bachma hainanensis S.-Y. Huang & Volynkin ssp. nov.

( Figs 1–6 , 16–18 , 24, 25 )

Barsine bachma bachma Volynkin et al. (2018 , partim): 1003.

Type material. Holotype ( Fig. 1 ): male, “ 25. X. 2018, Yinggeling, Qiongzhong Li & Miao Autonomous County, Hainan Province, P. R. China, leg. Zhi-peng Miao & Fu-hong Wei” [in Chinese ], gen. prep No.: H4 ( SCAU) . Paratypes ( Figs. 2–6 ): 1 male, 1 female, same data as for holotype, gen. prep No.: H3 (male) ( SCAU), 1 female, same locality and collector, but 22. X. 2018 ( SCAU); 1 female, 9–10. VII. 2018, Jianfengling National Park , Ledong Li Autonomous County, Hainan Province, P. R . China, gen. prep No.: H6 ( SCAU); 2 females, 6–7. VII. 2018, Yinggeling, Qiongzhong Li & Miao Autonomous County, Hainan Province, P. R . China, Shi-fang Mo & Fu-hong Wei leg., gen. prep No.: H1 ( SCAU); 1 male, 23. X. 2006, Atuoling, Mt. Wuzhi , Hainan Province, P. R . China, Zheng Li & Min Wang leg., gen. prep No.: H8 ( SCAU); 3 females, China, Hainan Isl., Wuzhi-Shan Mts. , 18°53′N, 109°43′E, 1500 m, 20.II.–10.IV.2001, local collector leg., ex coll. Dr. R . Brechlin, gen. prep No.: MWM 33569 Volynkin ( MWM / ZSM) .

Diagnosis. The forewing length is 8–9 mm (8 mm in the holotype) in male (n=3) and 10–11 mm in female (n=8). Externally, adults of both sexes of F. bachma hainanensis ssp. nov. are most similar to those of F. bachma bachma ( Volynkin & Černý, 2018) ( Figs. 7–9 , 19, 20 , 26 ) distributed in Vietnam, but male of the new subspecies can be distinguished by the somewhat wider and more diffuse postmedial streaks at the subapical area, whereas in male of F. bachma bachma the postmedial streaks are narrower and less diffuse at the subapical area. Females of the new subspecies can be distinguished from those of the nominate subspecies by the somewhat wider postmedial line of the forewing (especially at the costa), and somewhat more reddish hindwing ground color, whereas in female of F. bachma bachma , the postmedial line is generally narrower (especially at the costa) and the hindwing ground color is orange. Compared to F. bachma bolovena ( Volynkin & Černý, 2018) ( Figs. 10, 11 , 21 , 27 ) described from southern Laos, female of the new subspecies has the generally wider postmedial line of the forewing, and the less intense black suffusion in the subterminal and terminal areas of the hindwing. In the male genitalia, F. bachma hainanensis ssp. nov. can be easily distinguished from both continental subspecies by the spine-like medial costal process which is much shorter and distally narrower, whereas that of F. bachma bachma and F. bachma bolovena is conspicuously longer, blade-shaped and distally wider. The female genitalia F. bachma hainanensis ssp. nov. display no remarkable differences from those of F. bachma bachma , but have somewhat wider antevaginal plate with more rounded corners compared to F. bachma bolovena.

Distribution. Currently only known from Hainan Island, southern China. The nominate subspecies is known from Vietnam, and ssp. bolovena is known from southern Laos.

Etymology. The subspecific epithet refers to the type locality, Hainan Island in southern China.

Remarks. 1) In the original description of F. bachma, Volynkin et al. (2018) mentioned that the discal spot on forewing is absent in this species, whereas in the closely related F. punicea the spot is present except for females of certain subspecies. However, during the examination of further materials from Vietnam, we found a male of F. bachma bachma from central Vietnam ( Fig. 9 ) which has distinct discal spot on forewing. Similarly, in all the male specimens and most of the female specimens of F. bachma hainanensis ssp. nov., the discal spot is present, while in a few female specimens the discal spot is indistinct ( Fig. 5 ) or absent ( Fig. 6 ). Thus we conclude that the presence or absence of a discal spot in F. bachma is merely an individual variation and cannot serve as a diagnostic feature distinguishing it from F. punicea . The most reliable way to distinguish these two species is examining the genitalia of both sexes, where remarkable differences can be found. 2) Three females of F. bachma hainanensis ssp. nov. were wrongly included to the paratype series of F. bachma bachma by Volynkin et al. (2018), and herein they are reassigned to the paratype series of the new subspecies F. bachma hainanensis ssp. nov. 3)Although the medial costal process of Fossia bachma hainanensis ssp. nov. is significantly different from those of the other two subspecies, which might suggest a specific rank of the taxon, we still treat this population as a subspecies of F. bachma for the two reasons below. First, the shape of two important genitalia structures in the taxonomy of the genus Fossia , the juxta in male and the antevaginal plate in female are generally identical in bachma , bolovena and hainanensis ( Fig. 16–21 ) while differing from other congeners significantly. This suggests the conspecificity of these three taxa. As for the difference in the medial costal process, this process can sometimes be variable in length and width in other congeners, e. g. F. melanandra ( Černý, 2009) and F. elongata ( Volynkin & Černý, 2018) , as illustrated by Volynkin et al. (2018), thus we believe this character is not the diagnostic one in differentiate Fossia species while the shape of the juxta and the antevaginal plate are more crucial. However, since the shape of the medial costal process is stable in all the male specimens of Fossia bachma hainanensis ssp. nov. examined, we also consider this character to be a reliable difference to distinguish this new subspecies from the other two continental ones. Second, as stated in the Results part above, the genetic divergence between the Hainan population and F. bachma bachma from Indochina falls within the interspecific range of a single species. Overall, based on the morphological and molecular evidences, the best choice for treating Fossia population from Hainan currently is regarding it as a well-differentiate subspecies of F. bachma .

Figures

FIGURES 1–15. Fossia spp.: adults. Depositories of specimens: 1–5 in SCAU; 6, 14, 15 in MWM/ZSM; 7, 10, 11 in NHMUK (© The Trustees of NHMUK); 8 in CAV; 9, 12, 13 in CHSY; 1–3, 7, 9, 10, 12, 14: male, 4–6, 8, 11, 13, 15: female.

FIGURES 16–21. Male genitalia of different subspecies of Fossia bachma. Depositories of slides: 16–18 in SCAU; 19, 21 in NHMUK (© The Trustees of NHMUK); 20 in CHSY.

FIGURES 24–29. Female genitalia of Fossia spp. Depositories of slides: 24, 25 in SCAU; 26, 27 in NHMUK (© The Trustees of NHMUK); 28 in CHSY; 29 in MWM/ZSM.