Hydraena (Hydraenopsis) busuanga Freitag & Jäch, 2007

Freitag, Hendrik & Jäch, Manfred A., 2007, Revision of the species of Hydraena Kugelann (Coleoptera: Hydraenidae) from Palawan and Busuanga, with descriptions of eleven new species, and redescription of Hydraena (Hydraenopsis) scabra d’Orchymont, 1925, Zootaxa 1431, pp. 1-44 : 36-38

Hydraena (Hydraenopsis) busuanga Freitag & Jäch , sp. n.

(Figs. 13, 27a–h)

Type locality. Mabintangen River, five km northwest of Coron (town), Busuanga Island, Philippines.

Type material. Holotype ɗ ( UPLB): “ PHILIPPINEN: Palawan Pr. Busuanga Is., 5 km NW Coron Mabintangen Riv., 25.– 29.2.1996, leg. H. Zettel (82)”, terminal parts of abdomen, one maxillary palpus and one elytron glued separately, one mesotibia, one mesotarsus and aedeagus lacking. Paratypes: 1 ɗ ( NMW): same locality data as holotype; 1 Ψ (CZW): “ Philippinen: Palawan Pr. Busuanga Isl., 5 km NW Coron Mabentangen For.Res., 1.– 7.2. 1999, leg. H. Zettel (170)”.

Description. Body 1.40–1.55 mm long. Habitus as in Fig. 13. Head, pronotum and elytra chestnut brown; rectangular spot on pronotal disc dark brown; legs and maxillary palpi paler chestnut brown to reddish brown.

Maxillary palpi remarkably short, shorter than maximum width of pronotum.

Pronotum about twice as wide as long, broadest at the middle, subcordiform; pronotal disc densely punctate, interstices glabrous; postocular foveae and posterior discal foveae well impressed; anterior corners rounded; lateral margins slightly upturned, anteriorly convergently rounded, posteriorly distinctly sinuously convergent; lateral rim distinctly serrate; anterior margin concave, distinctly broader than biconcave posterior margin; area in front of posterior corner slightly impressed; pronoto-elytral angle almost rectangular; lateral portions of pronotum sparsely punctate, interstices more or less glabrous; hypomeron moderately impressed, distinctly broader than profemur, anterior portion rounded, not tapered, mesal portion narrow, hardly perceptible.

Elytra oval, conjointly rounded apically, with ca. 15 longitudinal, not very regular rows of punctures (nine between suture and shoulder); punctures small and deeply impressed; interstices and intervals glabrous; lateral portion widely explanate, reaching elytral apex; rim denticulate (posteriorly inconspicuously); inflexed lateral portion (pseudepipleuron) very wide (broader than metafemur), almost reaching elytral apex, with one row of punctures; epipleuron narrow, short, inconspicuous.

Mesoventrite with rather inconspicuous longitudinal ridges; mesoventral intercoxal process very slender, slightly wider than epipleuron; metaventral disc slightly impressed; metaventral plaques inconspicuous, pubescent; intercoxal sternite rather small, as long as broad, narrower than metafemur; metaventrite and ventrites 1–4 moderately densely pubescent.

Legs (tibiae in particular) more robust than in the other species; femora, meso- and metatibiae slightly curved.

Aedeagus ( Figs. 27 a–c) rather simple, slender. Main piece evenly and gently curved (lateral view), very slightly sinuous, almost straight (ventral/dorsal view), with one subapical dorsal seta (ca. nine micropores present); phallobase subsymmetric. Distal lobe not clearly delimited from main piece; ejaculatory duct distally ending in long, apically directed, tapering, slightly sinuous flagellum. Parameres short and slender, not articulately connected with main piece, inserted near middle of aedeagus (incl. flagellum), each with ca. seven moderately long setae at apex and ventral margin.

Gonocoxite ( Fig. 27 e) short, subcrescentic, strongly transverse; apical area of ventral plate moderately long, pubescent; setae of subapical tufts furcate; condyles retracted; dorsal plate rather complex, not surpassing outer plate, with two cavities.

Spermatheca as in Figs. 27 f–g.

Secondary sexual characters. Male profemora with conspicuous ventro-basal transverse ledge. Male terminal sternite subtrapezoidal; apical margin slightly rounded; base very broad, produced into small acute lateral appendages; spiculum gastrale about three times as long as sternite, slender, almost straight ( Fig. 27 d). Female tergite X ( Fig. 27 h) subsemicircular; disc with squamose setae, subapical fringe with trichoid setae; hyaline margin wide, medially notched.

Differential Diagnosis. Externally, Hydraena busuanga can be easily distinguished from all other known species of the Palawan Archipelago by its robust habitus, broad pronotum (about twice as broad as long), very broad elytral gutter, short palpi, short legs. Furthermore, its simple aedeagus with its long, apically directed, tapering, slightly sinuous flagellum is unique among Palawan/ Busuanga species. Female tergite X resembles H. zetteli , but its squamose setae are concentrated on the medial portion.

Etymology. Named after the island of Busuanga , Philippines, in reference to the geographical distribution.

Distribution ( Fig. 31 ). Known only from the type locality.

Ecology. This species was collected in a river of a forest reserve, which represents one of the very few relatively natural habitats on Busuanga Island. The fact that Hydraena busuanga could not be found in other sites in Busuanga suggests an ecological affinity for undisturbed habitats. This species is likely to be endemic to the Calamian group or even to Busuanga itself.

Figures

FIGURE 27. Hydraena busuanga sp. n. a – c) aedeagus (paratype from Mabintangen, Busuanga) in ventral, dorsal and lateral view; d) male sternite X and spiculum; e) gonocoxite; f – g) spermatheca; h) female tergite X.

FIGURE 31. Collecting sites and geographical distribution of Hydraena species in Palawan and Busuanga, including enlarged map of St. Paul National Park: Hydraena palawanensis sp. n., H. pseudopalawanensis sp. n., H. spp. ΨΨ cf. palawanensis / pseudopalawanensis, Hydraena sp. 1, H. manguao sp. n., H. hosiwergi sp. n., H. busuanga sp. n., Hydraena sp. 2, Hydraena sp. 3.