Larnaca, Walker, 1869

2. Larnaca View in CoL from mid-lower Red River montane region

The mid-lower Red River montane region mainly covers southeastern Yunnan, southwestern Guangxi of China, and northern Vietnam. To date, six species of Larnaca have been recorded from this region: Larnaca ( Larnaca) eugenii ( Griffini, 1914) , Larnaca ( Larnaca) vietnamensis Gorochov, 2003 , Larnaca ( Larnaca) nigricornis Ingrisch, 2018 , Larnaca ( Larnaca) tenuis Ingrisch, 2018 , Larnaca ( Larnaca) lieyongzhou Shen & Yin, 2022 and Larnaca ( Larnaca) nigrimacula Zhang, Zhang, Bian, 2023 .

However, these six species exhibit minimal interspecific differences. Only L. ( L.) lieyongzhou has distinct characteristics on the female seventh abdominal sternite; the external morphological traits of the other species are slightly differentiated. The diagnostic characters provided in their original descriptions primarily focus on the processes of the ninth abdominal tergite in males and body coloration. First, it is important to note that photographic angles can also introduce deviations in morphological observations—different angles may even result in different curvature of the processes on the ninth abdominal tergite of the same male individual ( Fig. 8 View FIGURE 8 ). Additionally, some species are distinguished solely by coloration. Nevertheless, the pronotal patterns of Larnaca are variable and should not be used as interspecific diagnostic characters. For example, the pronotal color of the holotype ( Yin & Meng, 2021) of Larnaca ( Larnaca) walle is inconsistent with that of its topotypes ( Figs. 7 View FIGURE 7 AB, 9F), and different individuals exhibit distinct color patterns. Shen & Yin (2022) also provided images of different pronotal color patterns of L. ( L.) lieyongzhou . Similarly, Yin & Shen (2023) noted variations in the intensity of pronotal patterns among different individuals of Larnaca ( Larnaca) lingcangensis .

Nevertheless, L. ( L.) tenuis only has a darker pronotum than L. ( L.) eugenii , while other traits are highly similar; the abdominal apex of the holotype of L. ( L.) tenuis also shows no significant differences. Furthermore, L. ( L.) nigricornis is also highly similar to L. ( L.) eugenii —the only differences are that the base of the teeth in L. ( L.) nigricornis is light-colored, and according to the original diagnosis, the processes on the ninth abdominal tergite in holotype of L. ( L.) nigricornis are slightly more curved. Additionally, L. ( L.) nigrimacula differs from these species only in the density of black spots on the vertex and pronotum, with no other obvious differences in diagnostic characters. These subtle, inconsistent distinctions—relying heavily on variable color traits or minor structural differences—make definitive species delineation challenging without direct comparison of a large amount of topotype specimens.

Regrettably, this study did not collect enough topotype specimens, so the discussion herein can only be based on photographic images. Further thorough field surveys, sampling, and analysis of the Larnaca species in this mountainous region are required, which may necessitate the synonymy of some species.