Hydraena (Hydraenopsis) hendrichi, 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 : 55-62

Hydraena (Hydraenopsis) hendrichi , new species

( Figs. 1 , 6 , 12 , 15 , 16 )

Type locality. — Shady pool in small ravine between Tuk Tuk and Tomok, Samosir Island, Lake Toba, North Sumatra, Indonesia .

Type material. — Holotype male ( NMW): “N-SUMATRA, 1990 Toba See [Lake], ca. 900 m Samosir , 3.2. leg. Jäch (1[crossed out with pen]+2)” . Paratypes: 9 exs. ( NMW), same label data as holotype ; 9 exs. ( NMW): “N-SUMATRA, 1990 (19) Sibolangit, Brastagi / Medan leg.Jäch, 25.2.” ; 6 exs. ( NMW): “ INDONESIEN 1991 (16) W-Sumatra, 25km E Padang NSG Taman Raya Bung Hatta 400m, leg. Jäch 14.2.” ; 5 exs. ( NMW): same locality and date, but “leg. Schödl ” ; 17 exs. ( NMW): “ INDONESIEN 1991 (18) W-Sumatra, Bungus Beach , 10m leg. Jäch 14.2.+23.2.” ; 2 males, 1 female ( ZSM): “ SINGAPORE, Bukit Timah swamp nr fishpond 9.IV.1997 Balke & Hendrich leg.” ; 1 female ( ZRC): “ SINGAPORE / Bukit Timah N.R., small stream n[ear]. entrance 9.4.1997 Balke & Hendrich leg.” ; 6 males, 11 females ( NMW, ZRC): “ Singapore, Bukit Timah NR. 9 Apr 1997. M Balke & L Hendrich” ; 4 males, 6 females ( ZRC): “ SINGAPORE: Bukit Timah NR. 9 Apr 1997. Balke & Hendrich leg.” ; 34 exs. ( NMW, ZSM): “ West Malaysia / JOHOR Bekok, path to waterfall 10. April 1997, 50– 150m Balke & Hendrich leg.” ; 1 ex. ( ZSM): “ West Malaysia / JOHOR Bekok, path to waterfall 10.IV. 1997, 50– 150 m Balke & Hendrich leg. Coll. HENDRICH” ; 15 exs. ( NMW): “ MALAYSIA: Pahang Tioman Island Umg. [surroundings] Kampung Tekek 16.- 24.7.1993 lg.Schuh” ; 13 exs. ( NMW): “ MALAYSIA: Pahang Tioman Island Kg.[Kampung] Tekek Umgebg. [surroundings] 15.- 26.7.1992 leg. R. SCHUH” ; 7 exs. ( NMW): “ Prov. PAHANG 28.1. Pulau Tioman (7) Tekek-Juara 80m ” / “ MALAYSIA 1992 leg. Schillhammer ” ; 1 male ( NMW): “ Malaysia, Pahang, Kuala Lipis env., Hutan Lipur Terenggun , 4. VI. 2001. Lake in secondary forest; shallow, warm, with poor subaquatic vege-tation.” ; 116 exs. ( CDL, CSH, ISNB, NMW): “ Malaysia, Johor [Pahang], Tioman Island 1.5 km E Juara, small stream in dense primary forest, 20. VI. 2001, J.F. Ko

iam lgt.”; 14 exs. ( NMW): “ Malaysia, Johor [Pahang], Tioman Island Tekek env., small stream in dense primary forest, 24. VI. 2001, J.F. Ko iam lgt.” ; 2 males, 3 females ( NMW): “ MALAYSIA 21.I.1992 SELANGOR: Templer Park, N K.L. [Kuala Lumpur] leg. Jäch (1)” ; 4 males, 2 females ( CSH): “S-THAILAND, Phangnga Prov., Thimung distr. , 5 km S Khao Lak 08°36'N, 98°15'E, 10–50 m, 03.-16.VIII.2012, leg. A. Skale ” ; 3 males, 1 female ( CWW): same locality, but “leg. A. Weigel ” ; 3 males, 3 females ( CSH): “S-THAILAND, Phang-nga Prov., Lamru distr. , 6 km NE Lam Kaen (white banana waterfall) 08°37.324'N, 98°18.362'E, 75 m, 13.VIII.2012, leg. A. Skale ” ; 2 males ( CWW): same locality, but “leg. A. Weigel ” .

Description. — Habitus as in Fig. 1 . Body length: 1.25–1.50 mm. Dorsum yellowish to reddish brown, frons dark brown, pronotum except of disc paler yellowish; maxillary palpi unicoloured yellow.

Labrum excised anteriorly; lobes rounded anteriorly, without corners. Clypeus sparsely punctate, smooth. Frontoclypeal suture very slightly arcuate, slightly impressed. Frons sparsely (middle) to moderately densely (laterally) punctate, interstices shining; interocular grooves more or less obsolete. Eyes large, protruding, more than 30 facets visible in dorsal view.

Pronotum very weakly cordiform, wider than long; anterior margin concave; anterior angles rounded; lateral rim slightly denticulate and very slightly produced at middle; disc rather flat, sparsely punctate, glabrous, foveae more or less obsolete; anterior, posterior and lateral portions of pronotum more densely punctate.

Elytra subparallel-sided; with about nine rows of punctures between suture and shoulder; punctures small, not deeply impressed, arranged in more or less regular, not impressed lines; intervals and interstices flat and glabrous; explanate margin of elytra weakly serrate posteriorly, narrow.

Foretibia slightly curved.

Mesoventral process wider than mesotibia. Metaventrite moderately deeply impressed between metaventral plaques, the latter convergent anteriorly, more or less ∧ -shaped ( Fig. 12 ).

Male terminal sternite and spiculum ( Fig. 6d ): Sternite pentagonal, slightly asymmetrical, base V-shaped, not firmly connected with spiculum.

Aedeagus ( Fig. 6a–c ): Main piece strongly asymmetrical in ventral view, dorsally with three long setae, which are conspicuously spiny in apical part; phallobase asymmetrical, not closed proximally. Distal lobe very large, intricately shaped, with numerous conspicuous spinules and bristles, flagellum long. Parameres articulately connected with main piece, inserted near phallobase. Left paramere elongate and slender, moderately long; dorsal margin with row of moderately long setae in apical half. Right paramere larger, wide; apex with very long, partly spiny setae; ventral margin with a row of about ten shorter, furcate setae.

Gonocoxite ( Fig. 6e ): Subtriangular, wider than long; lateral margins curved; inner plate slightly projecting sublaterally, with medially connected pair of caveae.

Female tergite X ( Fig. 6f ): Disc moderately densely covered with trichoid setae; subapical setae vermiform; posterior margin excised.

Spermatheca ( Fig. 6g –h ): Proximal portion sac-like; distal portion discoidal.

Secondary sexual characters: Male foretibia slightly more curved and with a small denticle on mesal face near apex. Male mesoventrite more deeply impressed between mesoventral disc and mesoventral process. Metaventral plaques of male distinctly ∧ -shaped ( Fig. 12 ), in female anterior part covered by setae, thus the two branches not distinctly contiguous anteriorly. Apex of male tergite X with small asymmetrical excavate projection.

Differential diagnosis. — Externally, Hydraena hendrichi can be distinguished easily from all other species from Singapore by the anteriorly convergent metaventral plaques. In addition, males of H. hendrichi possess a subapical denticle on the mesal face of the foretibia; in the only other species from Singapore with a denticle on the foretibia ( H. paulmoritz ), this denticle is not close to the apex.

Distribution. — South Thailand, Malaysia (Johor, Pahang, Selangor), Singapore ( Fig. 15 ), Indonesia (Sumatra).

In Singapore this species was collected only once, i.e. on 9 Apr. 1997 in the Bukit Timah Nature Reserve: in a small spring brook named Taban Valley ( Fig. 16 ) and in a swamp near a fish pond (see Balke et al., 1997: pl. 1, Fig. a). Since then it has never been found in Singapore again.

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

Figures

Figs. 1–4. Habitus of: 1, Hydraena hendrichi, paratype; 2, H. paulmoritz, paratype; 3, H. singaporensis, paratype; 4, H. yangae, holotype, right foreleg (lateral view) depicted separately (photograph taken before right elytron got unhinged).

Fig. 6. Hydraena hendrichi: a, aedeagus in lateral view; b, aedeagus, dorsal view; c, aedeagus, ventral view (setae of parameres omitted); d, male sternite X and spiculum; e, gonocoxite; f, female tergite X; g, h, spermatheca.

Figs. 12–14. Meso- and metaventrite of: 12, Hydraena hendrichi; 13, H. singaporensis; and 14, H. formula.

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

Fig. 16. Taban Valley, Bukit Timah Nature Reserve, Singapore. Three species, H. hendrichi, H. jacobsoni, and H. paulmoritz were collected from this site. (Photograph by: L. Hendrich).