Rivobates

Pešić, Vladimir, 2015, A new species of the water mite genus Hygrobates Koch, 1837 (Acari: Hydrachnidia: Hygrobatidae) from the ancient Lake Ohrid, Zootaxa 3926 (2), pp. 287-295 : 289

Key to the species of the subgenus Rivobates from the Western Palaearctic region

1 Genital field with a lower number of acetabula (5–10 pairs).................................................... 2

- Genital field with a higher number of acetabula (12–39 pairs, generally> 12)...................................... 4

2 (1) Males: Posterior margin of genital field strongly indented. Females: length of genital plates more than half the gonopore length, L ratio genital plate/gonopore> 0.6 Hygrobates diversiporus Sokolov, 1927 (Caucasus, Turkey)

- Males: Posterior margin of genital field straight or irregularly convex, but not indented. Females: length of genital plates about half the gonopore length, L ratio genital plate/gonopore <0.6................................................... 3

3 (2) Suture line Cx-III/IV strongly bowed near glandular opening on Cx-IV. Males: Anterior margin of genital field with a small, knob-shaped medial projection............... Hygrobates quanaticola Schwoerbel & Sepasgozarian, 1976 ( Iran; Turkey?)

- Suture line Cx-III/IV slightly bowed near glandular opening on Cx-IV. Males: Anterior margin of genital field without a projection............................................... Hygrobates zawali n. sp. (Lake Ohrid; Macedonia, Albania)

4 (1) Posteromedial margin of Cx-II pointed................................................................................................... Hygrobates psammocrenicus Gerecke & Di Sabatino, 2013 (peninsular Italy and Corsica)

- Posteromedial margin of Cx-II rounded.................................................................... 5

5 (4) P-4 ventral setae at the same level. Males: Posterior margin of genital field convex or straight. Females: Genital plates distinctly shorter than gonopore.......................... Hygrobates conspiciendus Biesiadka & Kowalik, 1978 ( Poland)

- P-4 ventral setae distanced from each other. Males: Posterior margin of genital field concave. Females: Genital plates as long as gonopore.......................................................................................... 6

6 (5) L P-3/P-4 ratio <0.60. Males: Genital field large, L/W 210–230/240–310. Female: Genital plates large, L/W 180–190/110–115................................... Hygrobates norvegicus (Thor, 1897) (Central, southern and south-eastern Europe)

- L P-3/P-4 ratio> 0.60. Males: Genital field smaller, L/W 165–186/188–264. Females: Genital plates smaller, L/W 135–150/ 70–80............................ Hygrobates helocrenicus Gerecke & Di Sabatino, 2013 (peninsular Italy and Sicily)