Dineutus, W. S. Macleay, 1825

Gustafson, Grey T., Hájek, Jiří & Miller, Kelly B., 2016, Description of two new species of Dineutus sensu stricto from Southeast Asia (Coleoptera: Gyrinidae) with a key to the known species of the subgenus, Acta Entomologica Musei Nationalis Pragae 56 (2), pp. 629-643 : 640-641

Key to the species of the Dineutus sensu stricto

Dineutus collarti Mouchamps, 1949 was originally described from specimens purported to be from northern Vietnam. In the original description MOUCHAMPS (1949) acknowledged that his species is nearly identical to D. regimbarti , but given their broadly separated localities, described the specimens as a new species. This species is very likely D. regimbarti but with specimens incorrectly localized. For this reason we have not included D. collarti in the key and suspend formal synonymization until examination of more D. regimbarti material.

1 Apicolateral sinuation of elytral apex distinct (Figs 8–11), apex in most species produced due to strong sinuation. .................................................................................................. 2

‒ Apicolateral sinuation of elytral apex very weak to imperceptible (Figs 12–14), apex not produced. ........................................................................................................................ 5

2 Species very robust in appearance, broadly oval with widest point just posterior of middle (Fig. 5); dorsoventrally very strongly convex especially in scutellar region; elytra with distinct preapical sericeous reticulation patch, elytral apices broadly rounded. Known from Lesser Sunda Islands Sumba and Timor. ............... D. regimbarti Régimbart, 1882

‒ Species less robust in overall appearance, more elongate oval; elytra with or without preapical sericeous reticulation patch. ........................................................................... 3

3 Habitus more elongate (Fig. 3). Elytra with distinct preapical sericeous reticulation patch, reticulation strongly impressed, sculpticells usually slightly transverse; pronotum with much less distinct lateral marginal depression. Apex of median lobe of aedeagus triangular, strongly pointed ( Fig. 18 ). Species only known from Sulawesi. ..................... .......................................................................................... D. brownei Mouchamps, 1949

‒ Habitus more oblong (Figs 1, 4). Elytra without distinct preapical sericeous reticulation patch, reticulation moderately impressed, sculpticells usually round; pronotum with well-developed lateral marginal depression. Apex of median lobe of aedeagus narrowly rounded ( Figs 19–20 ). Species not known from Sulawesi. ............................................ 4

4 Body form more attenuated anteriorly, especially in males (Fig. 1); in lateral view somewhat depressed, dorsoventrally not strongly convex; elytral apices broadly rounded with weaker apicolateral sinuation (Fig. 10). Apex of median lobe of aedeagus less acuminate ( Fig. 19 ). Widely distributed species in Sunda Islands. ........................................ ......................................................................................... D. politus W. S. Macleay, 1825

‒ Body form more evenly oval, broader in appearance (Fig. 4); in lateral view dorsoventrally much more convex, especially in scutellar region; elytral apices narrowly rounded with stronger apicolateral sinuation (Fig. 11). Apex of median lobe of aedeagus more acuminate ( Fig. 20 ). Species known only from Bali. ........................ D. barong sp. nov.

5 Habitus elongate oval, dorsoventrally flat. Body coloration green bronzy. Small species, body length 13.2 mm, known from single female from Sumatra [not studied]. ............... ......................................................................................... D. puellaris Mouchamps, 1949

‒ Habitus oblong, dorsoventrally convex. Body coloration olivaceous or blackish with bronzy lustre.................................................................................................................... 6

6 Habitus more regularly rounded (Fig. 2); elytra with indistinct preapical sericeous reticulation patch; elytral apices almost without apicolateral sinuation (Fig. 12). Median lobe of aedeagus narrow, regularly attenuated to broadly pointed apex ( Fig. 17 ). Species known from China, Laos, Vietnam and Japan. ...................... D. mellyi Régimbart, 1882

‒ Habitus rhomboid, distinctly attenuated anteriad and posteriad (Figs 6, 7); elytra without preapical sericeous reticulation patch; elytral apices with feeble apicolateral sinuation (Figs 13, 14). Species known from Thailand and Sumatra. ........................................... 7

7 Elytra distinctly expanded laterally just anterior to middle, giving dorsal habitus broadly rhomboid appearance (Fig. 7); in lateral view dorsoventrally relatively more depressed, strongest convexity in scutellar region, strongly depressed posteriorly, creating strong slope. Apex of median lobe of aedeagus broadly rounded ( Fig. 15 ). Species known from Sumatra. ............................................................................. D. fulgidus Régimbart, 1880

‒ Elytra not expanded laterally, much more regularly oval in dorsal habitus (Fig. 6); in lateral view dorsoventrally fairly strongly convex, convexity evenly distributed anteriorly and posteriorly. Apex of median lobe of aedeagus narrowly rounded ( Fig. 21 ). Species known only from northern Thailand. .................................................... D. sitesi sp. nov.

Figures

Figs 15– 23.15–21 lateral and dorsal view of the aedeagus of Dineutus s. str.species.15 – D. fulgidus Régimbart, 1880; 16 – D. regimbarti Régimbart, 1882; 17 – D. mellyi Régimbart, 1882; 18 – D. brownei Mouchamps, 1949; 19 – D. politus W. S. Macleay, 1825; 20 – D. barong sp. nov.; 21 – D. sitesi sp. nov. Scale bars = 1 mm. 22–23 male protarsus and mesotarsal claw: 22 – D. sitesi sp. nov.; 23 – D. barong sp. nov. Scale bars of protarsus = 1 mm, mesotarsal claw scale bars = 0.5 mm.