Hydrobaenus Fries

Key to species of Hydrobaenus Fries from the Russian Far East Males

1. Anal point reduced and usually in the form of rounded or triangular tubercle or projection............................ 2

- Anal point well developed.............................................................................. 6

2. Gonostylus wide, distally angularly, on the outer edge with small peakedness projection............................ 3

- Gonostylus different shapes, without projection on the outer edge............................................... 4

3. AR 2.50; LR1 0.73–0.74. Dorsocentrals 15–17. Transverse sternapodeme wide in middle part. Tergite IX narrowly triangular. Virga consists of 4 setae. Gonostylus nearest of megaseta with some setae of middle length..... H. laticaudus Saether, 1976

- AR 1.27; LR1 0.61.Dorsocentrals 4–5. Transverse sternapodeme narrow in middle part. Tergite IX rounded.Virga consists of 2 setae. Gonostylus nearest of megaseta with 2 strong and long setae........ H. tiunovi Makarchenko et Makarchenko, 2010

4. Gonostylus with tooth distally; inferior volsella double, with large rounded-triangular dorsal and ventral parts which well sep- arated from each other...................................................... H. biwaquartus Sasa et Kawai, 1987

- Gonostylus without tooth distally; inferior volsella different shapes and if consists of two parts, they not clearly separated... 5

5. Gonostylus straight, with large triangular or rounded triangular crista dorsalis in distal part. Virga consists of 4 setae. Acros-

tichals distally curved and beak-shaped....................................... H. kisosecundus Sasa et Kondo, 1991 - Gonostylus slightly curved, distally without crista dorsalis. Virga consists of 2 setae. Acrostichals simple.......................................................................................... H. fusistylus (Goetghebuer, 1933)

6. Gonostylus in apical part on the outer edge with a triangular or rounded-triangular projection......................... 7

- Gonostylus in apical part without projection................................................................ 8

7. Apical projection of gonostylus at angle pointing down. Virga consists of 4 setae. Transverse sternapodema with high rod-like oral projections.............................................................. H. conformis (Holmgren, 1869)

- Apical projection of gonostylus usually directed forward. Virga absent. Transverse sternapodema with low-triangular oral pro- jections................................................ H. pseudoconformis Makarchenko et Makarchenko, 2009

8. Gonostylus distally with crista dorsalis.................................................................... 9

- Gonostylus without crista dorsalis....................................................................... 12

9. Crista dorsalis triangular or rounded-triangular, located in apical inner edge and not always clearly visible behind megaseta. Tergite IX with a relatively long (about 33 µm) and narrow anal point. Acrostichals 0–5................................................................................. H. sigaensis Makarchenko, Makarchenko et Yavorskaja, 2009

- Crista dorsalis located on preapical inner edge. Acrostichals 22–24............................................. 10

10. Virga absent. Anal point parallel-sided or subparallel-sided, 28–40 µm long (Figs. 1–2, 3)................................................................................ H. distinctus (Makarchenko et Makarchenko, 2006) comb. n.

- Virga present. Anal point triangular, 16–24 µm long........................................................ 11

11. Gonostylus in apical quarter naked, crista dorsalis low and long, rounded or rounded-triangular. Dorsal part of inferior volsella rounded-triangular, ventral part long and flat................... H. sikhotealinensis Makarchenko et Makarchenko, 2006

- Gonostylus completely covered with microtrichiae, crista dorsalis short and rounded-triangular. Dorsal part of inferior volsella with finger-like projection, ventral part short and rounded.......... H. monodentatus Makarchenko et Makarchenko, 2005

12. Anal point wide and low, with a slightly concave apex. Inferior volsella large and rounded..................................................................................... H. septentrionalis Makarchenko et Makarchenko, 2005

- Anal point narrow and triangular. Inferior volsella different structure.......................................... 13

13. Inferior volsella weakly developed and as two low tuberculate projections.................................................................................................. H. parvacaudatus Makarchenko et Makarchenko, 2009

- Inferior volsella well developed... 14

14. Dorsal part of inferior volsella with finger-like or rounded apical projection (Figs. 30–33). AR 0.9–1.2................................................................................ H. jacuticus Makarchenko et Makarchenko, 2011

- Dorsal part of inferior volsella triangular or rounded, without projection. AR> 1.2................................ 15

15. AR 1.47–1.60. Anal point short (16–20 µm), with subapical pore. Dorsal part of inferior volsella rounded............................................................................... H. siricus Makarchenko et Makarchenko, 2005

- AR 2.0. Anal point more long (28 µm), without subapical pore. Dorsal part of inferior volsella triangular.......................................................................... H. maladistinctus Makarchenko et Makarchenko, 2009