Hydraena (Hydraenopsis) michaelbalkei, Jäch & Díaz & Skale, 2013

Jäch, Manfred A., Díaz, Juan A. & Skale, Andre, 2013, The Hydraenidae (Coleoptera) Of The Republic Of Singapore, Raffles Bulletin of Zoology 61 (1), pp. 53-71 : 65

Hydraena (Hydraenopsis) michaelbalkei , new species

( Figs. 8 , 15 )

Type locality. — Shaded pool with grass, 1°20.990’N, 103°48.677’E, near Sime Road , MacRitchie Reservoir, Singapore .

Type material. — Holotype male ( ZRC): “ SINGAPORE, Mac Ritchie , nr Sime rd, 24IV1997 Balke & Hendrich”. Maxillary palpi and legs missing.

Diagnosis. — Body length: 1.25 mm. This species is very closely related with Hydraena manguao Freitag & Jäch. Colouration , dorsal punctation and body form agree very well with the latter (see Freitag & Jäch, 2007: Fig. 11 ). Unfortunately, the legs of the holotype are missing and therefore we are (except for the sexually dimorphic male tergite X) at present not able to find any significant characters to distinguish H. michaelbalkei and H. manguao externally. Male tergite VIII apically distinctly produced.

Male terminal sternite and spiculum ( Fig. 8d ): Somewhat resembling a contrabass, more elongate than in H. manguao (Freitag & Jäch 2007: Fig. 25d); apex more widely rounded.

Aedeagus ( Fig. 8a–c ): In ventral and dorsal view distinctly Y-shaped as in H. manguao (Freitag & Jäch, 2007: Fig. 25a–c), H. sautakei Jäch & Díaz (Jäch & Díaz, 1999: Fig. 7 ) and H. miyatakei (Jäch & Díaz, 1999: Fig. 8 ). Main piece rather straight in lateral view; with only one short dorsal seta near base of distal lobe. Left paramere distinctly shorter than in H. manguao , distinctly thinner than in H. sautakei and H. miyatakei , with few apical setae; right paramere (as in H. sautakei and H. miyatakei ) completely fused to main piece, mainly indicated by the presence of two groups of setae.

Secondary sexual characters: Characters of male legs unknown. Male metaventral plaques thin and short (confined to basal half), carinate. Male tergite X with subapical, asymmetrically heart-shaped excavation; apex slightly excised, right corner longer than left one.

Etymology. — Named for Michael Balke (ZSM), excellent water beetle specialist, who collected the holotype (together with Lars Hendrich).

Distribution. — So far known only from Singapore (MacRitchie Reservoir), see Fig. 15 .

Figures

Fig. 8. Hydraena michaelbalkei: a, aedeagus in lateral view; b, aedeagus, dorsal view; c, aedeagus, ventral view; d, male sternite X and spiculum.

Fig. 15. Geographical map of Singapore, showing distribution of Hydraenidae.

Fig. 11. Hydraena paulmoritz: a, aedeagus in lateral view; b, aedeagus, dorsal view; aedeagus, ventral view; d, male sternite X and spiculum; e, gonocoxite; f, female tergite X; g, h, spermatheca.

Fig. 7. Hydraena yangae: a, aedeagus in lateral view; b, aedeagus, dorsal view (setae of left paramere omitted in a, b); c, aedeagus, ventral view (setae of right paramere omitted); d, male sternite X and spiculum; e, gonocoxite; f, female tergite X; g, h, spermatheca.