Hydraena (Hydraenopsis) yangae, 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 : 68-70

Hydraena (Hydraenopsis) yangae , new species

( Figs. 4 , 7 , 15 )

Type locality. — Sandy margin of a very shallow and slow flowing, shaded stream, 1°21'18"N 103°47'51"E, near Rifle Range Road , east of Bukit Timah, Singapore .

Type material. — Holotype male ( ZRC): “ SINGAPORE: (NS102) 417 ZRC.6.18870 Rifle Range Rd , 27.05.1993 leg. CM Yang et al.” The holotype is teneral; right foreleg detached and glued separately; apical tarsal segments of both forelegs lacking; right elytron not firmly attached to body.

Additional material examined. — MALAYSIA: 1 female ( NMW): Small tributary of Gombak River , above Jungle Lodge, N Kuala Lumpur, Selangor, 16 Feb.1993 ; 1 female ( ZSM): Path to waterfall, 50–150 m, Bekok, Johor, coll. M. Balke & L. Hendrich, 10 Apr.1997 .

Diagnosis. — Habitus as in Fig. 4 (holotype). Body length: holotype 1.05 mm, females from Malaysia 1.20 mm. This species is very closely related with H. okinawensis Jäch & Díaz and its allies ( H. satoi Jäch & Díaz , H. iheya Jäch & Díaz , H. victoriae Jäch & Díaz ) from the Ryukyu Archipelago (see Jäch & Díaz, 1999). Colouration yellowish to reddish brown, labrum, clypeus and pronotum paler than frons and elytra. The holotype of the new species can be distinguished from the Ryukyu species mainly by the lacking metaventral plaques, by the pro- and metatibiae and by the aedeagus.

Ventral face of protibia of holotype (see Fig. 4 ) widened in apical half, very slightly tapering to apex; metatibia hardly noticeably curved, posterior margin very slightly crested subapically.

Male terminal sternite and spiculum ( Fig. 7d ): Quite similar to those of H. hendrichi ; sternite more regularly pentagonal than in the latter, more or less symmetrical, apex straight, base V-shaped, not firmly connected with spiculum, which is thinner and longer than in H. hendrichi .

Aedeagus ( Fig. 7a–c ): Remarkably similar to H. okinawensis and its allies from the Ryukyu Archipelago (see Jäch & Díaz, 1999). Main piece conspicuously hooked apically (ventral/ dorsal view), with one long dorsal seta; phallobase almost symmetrical, forming a closed ring. Distal lobe elongate, large, not clearly delimited from main piece, with numerous conspicuous spinules. Parameres articulately connected with main piece, inserted in basal half of aedeagus. Left paramere elongate, slender, with two groups of setae on apex and ventral margin in apical third, some of these being furcate; right paramere oval in dorsal view, rather narrow and acute in lateral view, with two groups of setae, one on apex and one along ventral margin in basal two thirds.

The aedeagus of H. yangae can primarily be distinguished from the aedeagi of its relatives from Ryukyu by the main piece, which is wider in apical 0.3. Furthermore, it lacks a flagellum. However, the aedeagus of the holotype of H. yangae is quite teneral and it cannot be excluded that the flagellum got lost during preparation.

Gonocoxite ( Fig. 7e ): Closely resembling that of the H. okinawensis and its allies from the Ryukyu Archipelago, especially H. iheya . It is, however, more slender than in these species.

Female tergite X ( Fig. 7f ): Closely resembling H. okinawensis and its allies from the Ryukyu Archipelago, especially by the subacuminate apex and the conspicuous subapical sclerotisation. However, the disc lacks squamose setae.

Spermatheca ( Fig. 7g –h ): More or less as in the Ryukyu species.

Discussion: The females from Malaysia agree very well with the holotype, with which they share the wide mesosternal process and the lack of metaventral plaques. They are, however, more vividly coloured, because they are not teneral. They are very probably conspecific with the holotype, because it is unlikely, that two very closely related species occur in the same area. Bekok lies only 100 km NNW of Singapore.

Differential diagnosis. — Externally, this species closely resembles Hydraena singaporensis , especially in body size, body shape, colouration and lack of metaventral plaques. However, these two species are clearly distinguished by the width of the mesosternal process, by the male protibia, and by the male and female genital characters.

Distribution. — Singapore (Rifle Range Road, east of Bukit Timah), see Fig. 15 , Malaysia (Johor, Selangor).

Etymology. — Named for Chang-Man Yang, former curator of Insecta at the ZRC. She is doing a great job, even after

retirement. The holotype of this obviously rare species was collected by her.

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. 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.

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