Chalybion, Dahlbom, 1843

Pham, Phong Huy, Ohl, Michael, Nguyen, Anh Thi Tu & Nguyen, Dinh Thi, 2025, Taxonomy of the genus Chalybion Dahlbom, 1843 (Hymenoptera: Sphecidae) from Vietnam, with description of a new species, Zootaxa 5679 (4), pp. 573-584 : 582-583

Comments on Chalybion described by Abenis & Lit (2019)

In 2019, Abenis & Lit reviewed the genus Chalybion from the Philippines and described two new species, C. clarebaltazarae and C. stephenreyesi based on males only. They did not assign them to any species-group. For the former species, they stated that “Males of this species are close to Chalybion bengalense but can be differentiated from other Chalybion species by the presence of placoids in flagellomeres 7 to 9”. However, Hensen (1988) has already shown that placoids in C. bengalense occur on flagellomeres 5 or 6 to 9, and in C. japonicum on flagellomeres 8 and 9. In C. bengalense and C. japonicum we have studied placoids are present on flagellomeres 5 or 6 to 9 ( Figs 1, 4 ) and 7 or 8 to 9 ( Figs 12, 15 ), respectively. Thus, it is clear that the distribution of placoids is variable and that the placoid pattern is not a reliable diagnostic character to distinguish species of Chalybion . For the latter species, Abenis & Lit stated that “This species is close to Chalybion bengalense but can be easily differentiated by the absence of plantulae. Males are easily recognized by the presence of placoids on flagellomeres 5 to 8”. They attributed to C. bengalense the presence of tarsal plantulae (see also their key to Chalybion ). Furthermore, they stated that the morphology of genitalia in C. bengalense is variable. Both Hensen (1988) and Anagha et al. (2022) show that tarsi of C. bengalense have no plantulae. Chalybion bengalense from Vietnam also lack tarsal plantulae and there is no variation of genitalia in both C. bengalense ( Figs 2, 3, 5, 6 ) and C. japonicum ( Figs 13, 14, 16, 17 ). Another important fact is that in C. bengalense the apex of the gonostyle has dense, long setae ( Figs 2, 3, 5, 6 ) (see also Fig. 128 in Hensen (1988)), that lack from Abenis & Lit’s Fig. 1 .

In summary, we conclude that the descriptions of C. clarebaltazarae and C. stephenreyesi by Abenis & Lit (2019) are based on variable characters, which are not suitable for species delimitation in Chalybion . It seems likely that both species are junior synonyms of already described species. However, a careful examination of the type materials is needed to confirm their identity.

Figures

FIGURES 1–6. Antenna and genitalia of male Chalybion bengalense (Dahlbom, 1845), ♂♂. 1. Antenna with placoids on flagellomeres 5–9; 2. Genitalia, in ventral view; 3. Genitalia, in dorsal view; 4. Antenna with placoids on flagellomeres 6–9; 5. Genitalia, in ventral view; 6. Genitalia, in dorsal view. Arrows show position of placoids.

FIGURES 12–17. Antenna and genitalia of male Chalybion japonicum (Gribodo, 1882), ♂♂. 12. Antenna with placoids on flagellomeres 7–9; 13. Genitalia, in ventral view; 14. Genitalia, in dorsal view; 15. Antenna with placoids on flagellomeres 7–9; 16. Genitalia, in ventral view; 17. Genitalia, in dorsal view. Arrows show position of placoids.