Hydraena (Hydraenopsis) singaporensis, 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 : 67-68

Hydraena (Hydraenopsis) singaporensis , new species

( Figs. 3 , 5 , 13 , 15 , 17 )

Type locality. — Stream in Upper Peirce Forest , Singapore .

Type material. — Holotype male ( ZRC): “ SINGAPORE: 424 Y774 Upper Pierce [Peirce] Forest, ‘J’ stream 31.10.1991 leg. DH Murphy et al” . Paratypes: 2 females ( NMW, ZRC), same locality data as holotype ; 1 female ( ZRC): “ Singapore Nee Soon Swamp Forest , 30. Apr. 1992 Coll. KL Yeo, Bengkeng ” ; 10 exs. ( NMW, ZRC): “ SINGAPORE, Nee Soon Swamp-forest 21 Apr 1997 \ Balke & Hendrich” ; 5 exs. ( ZRC): “ Singapore: Nee Soon Swampforest. 21 Apr 1997. M Balke & L Hendrich” ; 2 males, 1 female ( ZSM): “ SINGAPORE: 21.- 28.4.1997 Nee Soon Swamp Forest flight intercept trap leg. Balke & Hendrich ” ; 1 female ( ZSM): “ SINGAPORE / Nee Soon Swamp Forest , small path n[ear]. pipeline, 21.- 28.4. 1997 Flight Intercept Trap Balke & Hendrich leg.” ; 1 male, 1 female ( NMW): “ SINGAPORE McRitchie Reservoir preserve area, 19.1.2002, leg. Zettel (SG4)” .

Description. — Habitus as in Fig. 3 . 1.05–1.25 mm long. Dorsum unicoloured reddish brown to dark brown, or head

and/or pronotum paler yellowish brown; maxillary palpi always unicoloured yellowish.

Labrum excised anteriorly, very sparsely punctate. Clypeus sparsely punctate and smooth medially. Fronto-clypeal suture 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 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, disc with a pair of shallow basal impressions, which are sometimes connected by shallow transverse groove; anterior, posterior and lateral portions of pronotum more densely punctate.

Elytra suboval, 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 narrow, hardly noticeably denticulate apically.

Mesoventral process ( Fig. 13 ) about as wide as mesotibia. Metaventrite ( Fig. 13 ) moderately deeply impressed, metaventral plaques absent.

Male terminal sternite and spiculum ( Fig. 5d ): Sternite subrectangular, longer than wide, apical half asymmetrical, firmly connected with spiculum.

Aedeagus ( Fig. 5a–c ): Main piece strongly angulate in lateral view (basal and apical part forming a right angle), apical part long and slender, almost straight, without setae, ventral margin of basal part with conspicuous spine; phallobase subsymmetrical. Distal lobe moderately large, inserted near angle between basal and apical part of main piece, not reaching apex of main piece, with an extraordinary long, thin, coiled flagellum. Parameres articulately connected with main piece, inserted near phallobase. Left paramere very short, suboval, with about five apical setae. Right paramere elongate and slender, club-shaped, reaching middle of main piece; apex with about four moderately long setae, lateral face with short spines.

Gonocoxite ( Fig. 5e ): Subtriangular, approximately as wide as long; lateral margins curved; inner plate hardly noticeably projecting sublaterally.

Female tergite X ( Fig. 5f ): Subsemicircular, disc moderately densely covered with trichoid setae; subapical setae also trichoid, vermiform setae absent; posterior margin excised.

Spermatheca ( Fig. 5g –h ): Proximal portion crescentic, with sickle-shaped transverse crest in the middle; distal portion discoidal; spermathecal duct very long and conspicuously coiled.

Secondary sexual characters: Male foretibia very slightly curved. Male mesoventrite more deeply impressed between mesoventral disc and mesoventral process. Male tergite X excised apically, asymmetrical (left lobe wider and longer).

Variability: The variability in the colouration of the dorsum is quite remarkable. The three specimens from Peirce Forest are unicoloured, whereas all other specimens are more or less distinctly bicoloured. This may, however, be attributed to tenerality rather than to genetic differences. The three specimens from Peirce Forest were collected in October, while the remaining specimens were collected from January to April, some of these being distinctly teneral.

Differential diagnosis. — Externally, Hydraena singaporensis can be recognised by the combination of the following characters: small body size, mesoventral process not wider than mesotibia, metaventral plaques lacking.

Distribution. — So far known only from Singapore (Upper Peirce Forest, Nee Soon Swamp Forest, MacRitchie Reservoir), see Fig. 15 .

Etymology. — This species named in reference to the type locality.

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. 5. Hydraena singaporensis: a, aedeagus in right lateral view; b, aedeagus, ventral view (flagellum not depicted completely in a, b); c, aedeagus, left lateral view; 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. 17. Nee Soon Swamp Forest, Singapore; C.M. Yang on right. Four species, H. formula, H. jacobsoni, H. paulmoritz, and H. singaporensis were collected from this site. (Photograph by: L. Hendrich).