Peltocercyon vagus (Sharp, 1884) Mai & Jia & Ryndevich & Angus & Minoshima & Fikáček & Růžička, 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 : 12-13

publication ID	https://doi.org/10.11646/zootaxa.5671.1.1
publication LSID	lsid:zoobank.org:pub:60D33D8C-BDC2-4C2A-B840-90014815E8CB
persistent identifier	https://treatment.plazi.org/id/1032930E-FF89-6B20-FF2C-20B5B685EC98
treatment provided by	Plazi
scientific name	Peltocercyon vagus
status

Treatment

Peltocercyon vagus group

Peltocercyon ohoni Hoshina, 2021 . Japan (Honshu).

Peltocercyon sanaii ( Hoshina, 2008) , comb. nov. (from Cercyon View in CoL ). Japan (Honshu, Shikoku).

Peltocercyon shigehisai Hoshina, 2018 View in CoL . Japan (Hokkaido).

Peltocercyon subopacipennis (Nakane, 1965) View in CoL . Japan (Honshu).

Peltocercyon vagus (Sharp, 1884) , comb. nov. (from Cercyon ). Japan (Honshu), Russia (Russian Far East, Kunashir Island), South Korea.

A key to species of genus Peltocercyon

The species of the P. vagus group (i.e., those from Japan, Russian Far East and Korea) are not revised here in detail due to limited material available, and they are hence keyed as ʻ P. vagus groupʼ only. See below under this group for more details.

1 Middle part of prosternum separated from lateral portions by a ridge ( Fig. 2B, C View FIGURE 2 ). Mesoventral plate subtriangular ( Fig. 2B View FIGURE 2 ) or spindle-shaped ( Fig. 2C View FIGURE 2 )............................................................................... 2

- Prosternum without ridges dividing its median portion from lateral parts ( Fig. 2A View FIGURE 2 ). Mesoventral plate spindle-shaped...... 3

2 Mesoventral plate subtriangular, broadly contacting anterior part of metaventrite ( Fig. 2B View FIGURE 2 ). Prosternum with a pair of distinct oblique ridge on each side ( Fig. 2B View FIGURE 2 ); prosternal process deeply notched posteriorly ( Fig. 2B View FIGURE 2 ). Antennal grooves narrow ( Fig. 10B View FIGURE 10 ). Head with moderately large posterior tentorial pits ( Fig. 10A View FIGURE 10 )..................... P. coomani d'Orchymont, 1925 View in CoL

- Mesoventral plate spindle-shaped, contacting the anterior part of metaventrite in a single point ( Fig. 2C View FIGURE 2 ). Prosternum with a pair of curved fine ridges on each side ( Fig. 2C View FIGURE 2 ); prosternal process pointed posteriorly ( Fig. 2C View FIGURE 2 ). Antennal grooves large ( Fig. 2C View FIGURE 2 ). Head with large and deep posterior tentorial pits ( Fig. 8A View FIGURE 8 )................................ .. P. carnarius sp. nov.

3 Elytra dull; surface between punctures densely dotted or microreticulate ( Fig. 4C–F View FIGURE 4 )................................ 4

- Elytra shiny; surface between punctures smooth ( Fig. 4A, B View FIGURE 4 )................................................... 5

4 Spaces between elytral ground punctures microreticulate ( Fig. 4E, F View FIGURE 4 ). Arcuate ridge of metaventrite strongly bent backwards and distinct even laterally ( Fig. 30E View FIGURE 30 ). Paramere of aedeagus slightly expanded and rounded apically ( Figs 29D, F View FIGURE 29 , 31I View FIGURE 31 1 View FIGURE 1 )............................................................................................. P. vagus group

- Spaces between elytral ground punctures with very dense and tiny dots ( Fig. 4C, D View FIGURE 4 ). Arcuate ridge of metaventrite slightly bent backwards, almost transverse at the anterolateral corner, weakly developed laterally of the femoral line ( Fig. 18E View FIGURE 18 ). Paramere of aedeagus strongly expanded and obliquely truncate apically ( Fig. 17D, F View FIGURE 17 )....................... P. rugosipennis sp. nov.

5 Punctation of pronotum consisting of crescent-shaped punctures of uniform size.................................... 6

- Punctation of pronotum consisting of two sizes of punctures, the finer punctures crescent-shaped, the coarser punctures rounded ( Fig. 12A View FIGURE 12 ).......................................................................... P. kouwenkaii sp. nov.

6 Dorsum uniformly reddish brown to black ( Figs 5A View FIGURE 5 , 19A View FIGURE 19 ). Lateral area of metaventrite with scattered coarser punctures ( Figs 6D View FIGURE 6 , 20C View FIGURE 20 ). First abdominal ventrite with short longitudinal sculptures basally ( Figs 6E View FIGURE 6 , 20D View FIGURE 20 ). Paramere of aedeagus expanded and broad apically, with a rounded or truncated apex; inner face of the paramere without fringe of setae................. 7

- Parts of elytra or pronotum with distinct darker or lighter patches ( Figs 15A–C View FIGURE 15 , 21A, D View FIGURE 21 , 23A View FIGURE 23 , 25A, D View FIGURE 25 , 27A View FIGURE 27 ). Lateral area of metaventrite without coarse punctures. First abdominal ventrite without basal longitudinal sculptures. Paramere of aedeagus slightly widened subapically and then gradually narrowing towards apex, with a bluntly pointed apex; inner face of the paramere with a fringe of long setae subapically..................................................................... 8

7 Dorsum dark reddish brown ( Fig. 19A View FIGURE 19 ). Middle portion of prosternum finely rugose ( Fig. 20B View FIGURE 20 ). Anterior ridge of metaventrite continuous with the arcuate ridge at the crossing point of femoral line ( Fig. 20C View FIGURE 20 ). Paramere of aedeagus slightly expanded apically ( Fig. 19F View FIGURE 19 )............................................................ P. vividus ( d'Orchymont, 1925)

- Head and pronotum dark reddish brown; elytra reddish brown to black ( Fig. 5A View FIGURE 5 ). Middle portion of prosternum rugulose ( Fig. 6B View FIGURE 6 ). Anterior ridge of metaventrite discontinuous with the arcuate ridge at the crossing point of femoral line ( Fig. 6D View FIGURE 6 ). Paramere of aedeagus distinctly expanded apically ( Fig. 5F View FIGURE 5 ).................................. P. basirugosus sp. nov.

8 Elytra with black patches lateromedially ( Figs 15A–D View FIGURE 15 , 21A, B, D View FIGURE 21 , 23A, B View FIGURE 23 , 25A, B, D View FIGURE 25 , 27A, B View FIGURE 27 ). Head with posterior tentorial pits small............................................................................................ 9

- Elytra black with yellow brown on posterior half ( Fig. 13A, B View FIGURE 13 ). Head with large posterior tentorial pits ( Fig. 14A View FIGURE 14 )............................................................................................. P. latifossus sp. nov.

9 Head completely black dorsally. Pronotum with black-yellow pattern. Elytra yellowish to reddish brown, each elytron with a large triangular lateral black spot, elytral interval 1 black ( Figs 21 View FIGURE 21 , 23 View FIGURE 23 , 25 View FIGURE 25 , 27 View FIGURE 27 ) ( Peltocercyon splendidu s-group)......... 10

- Head black with a median yellow brown spot. Pronotum uniformly yellowish brown. Elytra yellowish brown, with a continuous or discontinuous V-shaped black patch across the disc, elytral interval 1 slightly darkened ( Fig. 15A–D View FIGURE 15 ).................................................................................... P. lunulatus ( Gemminger & Harold, 1868) View in CoL

10 Pronotum black medially and yellowish to reddish brown laterally, the black median area wider or narrower ( Figs 23A View FIGURE 23 , 25A, D View FIGURE 25 , 27A View FIGURE 27 ). Antennal grooves narrow to moderately large ( Figs 24B View FIGURE 24 , 26B View FIGURE 26 , 28B View FIGURE 28 )..................................... 11

- Pronotum yellowish to reddish brown, with an M-shaped large black spot on disc ( Fig. 21A, D View FIGURE 21 ). Antennal groove broad ( Fig. 22B View FIGURE 22 )............................................................................. P. maculipennis sp. nov.

11 Median black spot of pronotum wide, yellowish brown parts present only laterally................................. 12

- Median black spot of pronotum narrow, leaving most of pronotal surface yellowish brown ( Fig. 27A View FIGURE 27 )... P. taylorae sp. nov.

12 Triangular black patches on elytra reaching suture and connected in the middle ( Fig. 23A View FIGURE 23 ). Median lobe of aedeagus broad and almost paralleled laterally ( Fig. 23E View FIGURE 23 ).................................................... P. medogensis sp. nov.

- Triangular black patches on elytra reaching elytral stria 3, not connected in the middle ( Fig. 25A View FIGURE 25 ). Median lobe of aedeagus slender, widest in the middle and gradually narrowing towards apex ( Fig. 25F View FIGURE 25 )................... P. splendidus sp. nov.

Species treatments