Peltocercyon vagus (Sharp, 1884), 2025

Mai, Zuqi, Jia, Fenglong, Ryndevich, Sergey K., Angus, Robert, Minoshima, Yûsuke N., Fikáček, Martin & Růžička, Jan, 2025, Taxonomic Revision and Phylogeny of the Genus Peltocercyon d'Orchymont, 1925 (Coleoptera: Hydrophilidae: Megasternini), Zootaxa 5671 (1), pp. 1-74 : 54-55

Peltocercyon vagus (Sharp, 1884) , comb. nov.

Fig. 31A–G

Cercyon vagus Sharp, 1884: 459 . Type locality: Japan ( Oyama , Kanagawa Pref.).

Cercyon (Conocercyon) vagus Sharp, 1884: 318 . Ryndevich, 2006.

Type material examined. Lectotype ( Fig. 31A–E ): female ( NHMUK) “ Cercyon vagus , Type D.S. / Oyama , Japan / Lewis (Sharp’s hand writing) // Type // SYN-TYPE // Lectotypus ♀ Cercyon vagus sharp / design. Shatrovskiy, 1987// Lectotypus 2005 / Cercyon vagus sharp /design. Ryndevich S.” Paralectotype ( Fig. 31F, G ): female ( NHMUK) “ Japan. / G. Lewis. / 1910–320. // Miyanoshita. / Cercyon vagus D.S. / SYN-TYPE // Paralectotypus 2005 / Cercyon vagus sharp /design. Ryndevich S.”

Additional material: 1 spec. ( SKRC) “ Russian far East, Kunashir Is., near Mendeleevo, 16– 17.9.1975, leg. Korotyaev B.A. ” ; 1 spec. ( SKRC) “ Kunashir , 15 km Yu Sernovodska [south of Sernovodsk], 7 vi [19]93, [leg.] I.M. Kerzhner ” [in Russian] ; 1 spec. ( SKRC) “YuZ [ Southwest ] Kunashir, cordon Ozerny, 21–28. vii.2011, [leg.] SA Kurbatov” [in Russian] ; 6 spec. ( SKRC), “Rossiya [ Russia], o [isl.] Kunashir , nizhnee techenie r. [lower reaches of river] Saratovskaya River, 12– 18.07.2014, leg. Yu. Sundukov, [in Russian].”

Remarks. Sharp (1884) described Cercyon vagus based on two female specimens collected from Oyama and Miyanoshita, Japan. In the original description, the species was characterized by deeply impressed elytral striae and convex intervals, though no details were provided regarding the ventral morphology. Ryndevich (2006) placed this species in the subgenus Conocercyon Hebauer, 2003 , based on the presence of arcuate ridges on the anterolateral corners of metaventrite. We examined two type specimens and revealed that the species also has complete femoral lines on the metaventrite that cross the anterolateral arcuate ridges at the anterolateral corners of metaventrite, i.e. the diagnostic character of Peltocercyon ( Fig. 31E ). Moreover, the species closely resembles other Japanese Peltocercyon species by external morphology. We therefore transfer the species from Cercyon to Peltocercyon . Peltocercyon vagus can be distinguished from P. sanaii ( Hoshina, 2008) , comb. nov., and P. subopacipennis (Nakane, 1965) by the sparse microreticulation between the ground punctation on the elytra, which makes the elytra less opaque ( Fig. 31D ) (the elytra in the latter two species are densely microreticulate and much more opaque; Fig. 32A, C ).

Distribution ( Fig. 41 ). Japan (Honshu), Russia (Russian Far East, Kunashir Island), South Korea ( Hansen 1999, Ryndevich 2006, Ryndevich et. al. 2021).

Figures

FIGURE 31. Peltocercyon vagus (Sharp, 1884). A–E: lectotype and its labels. F, G: paralectotype of Cercyon vagus sharp, 1884) and its labels. H, I: specimen from Kunashir Island. A: dorsal view. B: ventral view. C: specimen and its labels. D: detail of elytra. E: detail of ventral view. F: dorsal view. G: labels. H: dorsal view. I: male genitalia (1: tegmen. 2: median lobe. 3: sternite 9).

FIGURE 32. Type specimens of Cercyon sanaii (Hoshina, 2008) and Peltocercyon subopacipennis (Nakane, 1965). A, B: holotype of Cercyon sanaii. C–E: holotype of Peltocercyon subopacipennis and its labels. F–I: paratype of P. subopacipennis and its labels. A: dorsal view. B: ventral view. C: dorsal view. D: lateral view. E: labels. F: ventral view. G: labels. H: ventral view. I: labels.

FIGURE 41. Distribution map of species in Peltocercyon vagus group.