Hydraena labropaca, Perkins, 2011

Perkins, Philip D., 2011, New species (130) of the hyperdiverse aquatic beetle genus Hydraena Kugelann from Papua New Guinea, and a preliminary analysis of areas of endemism (Coleoptera: Hydraenidae) 2944, Zootaxa 2944 (1), pp. 1-417 : 98

Hydraena labropaca , new species

( Figs. 167 , 169, 511 )

Type Material. Holotype (male): Central Province: nr. Port Moresby, Sogeri Plateau, Musgrave River , river, [GE est.] 100–200 m, 9° 46' S, 147° 41' E, 16 iii 1965, M. E. Bacchus (MEB 200) ( NHM) . Paratypes (21): Sandaun Province: Mianmin , 670 m, 4° 53.329' S, 141° 35.263' E, 22 x 2008, S. Ibalim ( PNG 189) (1 ZSM) ; Mianmin [Miyanmin], [GE est.] 700–800 m, 4° 54' S, 141° 36' E, 19–21 v 1998, A. Riedel (3 NMW) ; Mianmin , pool, 990 m, 4° 54.57' S, 141° 35.49' E, 23 x 2008, S. Ibalim ( PNG 193) (1 ZSM) ; Mianmin , river, 700 m, 4° 52.858' S, 141° 31.706' E, 21 x 2008, S. Ibalim ( PNG 197) (5 ZSM) ; Mianmin , river, 1080 m, 4° 55.78' S, 141° 38.185' E, 24 x 2008, S. Ibalim ( PNG 195) (6 MCZ, NHM, NMW, PNG, ZSM) ; Ofektamin , 820 m, 5° 4.113' S, 141° 35.841' E, 17 x 2008, S. Ibalim ( PNG 190) (4 ZSM) ; S Mianmin , stream, 700 m, 4° 54' S, 141° 36' E, 19 v 1998, A. Riedel (1 NMW) .

Differential Diagnosis. Among members of the Cristatigena group, similar to H. inplacopaca and H. transvallis in the absence of metaventral plaques; differing from H. inplacopaca in the smaller size (ca. 1.62 vs. 2.07 mm), the less dense but slightly coarser pronotal punctation, and the less apparent dorsal setae; differing from H. transvallis by the larger elytral granules and the simple mesotibiae ( Figs. 167 , 170 , 171 ). Males are differentiated from all other members of the Cristatigena group by the distinctively modified labrum. The male genitalia of the three species share a basic form, but differ in several significant details ( Figs. 169, 172, 173).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.62/0.73; head 0.26/0.40; pronotum 0.37/0.51, PA 0.46, PB 0.43; elytra 0.98/0.73. Dorsum dark brown, head and pronotal disc piceous, palpi light brown, except distal 1/2 of last palpomere darker.

Dorsum of head and pronotum densely punctulate, dull; punctures of frons disc and pronotal disc ca. 1xef, interstices ca. 1xpd or slightly larger; punctures of clypeus obsolete. Labrum wide but short, lateral angles sharply rounded, anterior margin angulate and with small point on each side of deep V-shaped apicomedian excision, free margins moderately upturned. Mentum sparsely, moderately coarsely punctate, weakly shining; postmentum anterior 1/2 with punctation similar to mentum, posterior 1/2 densely micropunctulate. Genae raised, posterior ridge strong. Pronotum with anterior margin weakly emarginate over middle 1/2; all pronotal foveae moderately deep; PF2 very narrowly separated from one another.

Elytra subrugulose, dull, punctures very indistinct, each puncture with three granules, one at anterior margin and one on each side. Intervals not raised, width ca. 1xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins not forming angle with one another. Explanate margin well developed, about as wide as widest part of metatibia.

Metaventrite markedly tumid on each side of median impression, plaques absent, hydrofuge pubescence dense. P1 laminate; median carina sinuate in profile. P2 moderately narrow, l/w ca. 2/1, sides parallel, apex blunt. No midlongitudinal carina between mesoventral intercoxal process and median impression. AIS flat, width at straight posterior margin ca. 2x P2. Protibia (male) widened, weakly arcuate, medial surface flat; mesotibia simple; metatibia very gradually widening from base to apex, very weakly arcuate. Abdominal apex symmetrical.

Aedeagus ( Fig. 169) main piece with comparatively small (for group) distal lobe, in ventral aspect, arching from right side toward left side, apically with two small rounded lobes; left paramere as large as distal lobe, widest at midlength, with two small lobes, each with a cluster of setae; right paramere longer than and apically slightly wider than distal lobe of main piece; distal piece, in right lateral view, with large lobe of characteristic shape.

Etymology. Named in reference to the sexually dimorphic labrum, and the relationship to H. variopaca .

Distribution. An unusual, very disjunct distribution: several narrowly separated localities near Mianmin, in far western Area 1 (700–1080 m), and one locality far south, near Port Moresby, in Area 11 (100–200 m) ( Fig. 511 ).

Notes. Males from Mianmin, Sandaun Province: differ from the holotype in the following characters: the labrum is shaped very slightly differently; the metatibiae have a slightly more pronounced increase in width in the distal 1/2, and a slightly deeper emargination on the medial margin, just before the enlargement; the right paramere of the aedeagus is apically more truncate.

Figures

FIGURE 167. Hydraena labropaca, holotype, dorsal and lateral habitus, and venter.

FIGURE 170. Hydraena implacopaca, holotype, dorsal and lateral habitus, and venter.

FIGURE 171. Hydraena transvallis, holotype, dorsal and lateral habitus, and venter.

FIGURES 511–514. Geographical distributions of Hydraena species.