Hydraena paxillipes, 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 : 61-62

Hydraena paxillipes , new species

( Figs. 91 , 93, 319–321 , 472 )

Type Material. Holotype (male): Morobe Province: Lae–Bulolo road, Patep Creek , ex gravel bank of large fast river, [GE est.] 900–1100 m, 6° 52' S, 146° 37' E, 28 xii 1964, M. E. Bacchus (MEB 126) ( NHM) . Paratypes (52): Madang Province: Akameku– Brahmin , Bismarck Range, 750 m, 5° 49.307' S, 145° 24.389' E, 25 xi 2006, Balke & Kinibel ( PNG 114) (1 ZSM) ; Finisterre Mts. , Naho River Valley, Damanti, ex gravel banks of very fast-running clear stream, 914 m, 5° 55' S, 145° 58' E, 11 x 1964, M. E. Bacchus (MEB 47) (10 NHM) ; Ramu Valley , Sare River, 4 km N Brahman, [GE est.] 130–150 m, 5° 39' S, 145° 22' E, 16 iv 1991, D. Larson (10 MCZ) ; Morobe Province: Lae–Bulolo road, ex muddy gravel bank of small shaded stream, [GE est.] 900–1100 m, 6° 52' S, 146° 37' E, 28 xii 1964, M. E. Bacchus (MEB 125) (16 NHM) ; Lae–Bulolo road, Gurakor Creek, ex gravel banks, [GE est.] 900–1100 m, 6° 50' S, 146° 37' E, 30 xii 1964, M. E. Bacchus (MEB 133) (5 NHM) ; Lae–Bulolo road, Patep Creek, ex gravel bank of large fast river, [GE est.] 900–1100 m, 6° 52' S, 146° 37' E, 28 xii 1964, M. E. Bacchus (MEB 126) (4 NHM) ; Lae , Umg. [=environs of] Oomsis, Buang River, [GE est.] 20–30 m, 6° 53' S, 146° 57' E, 14 vi 1979, W. G. Ullrich (1 NHM) ; Sandaun Province: Mianmin , river, 700 m, 4° 52.858' S, 141° 31.706' E, 21 x 2008, S. Ibalim ( PNG 197) (1 ZSM) ; Mianmin , river, 1080 m, 4° 55.78' S, 141° 38.185' E, 24 x 2008, S. Ibalim ( PNG 195) (4 ZSM) .

Differential Diagnosis. Among members of the Colorata group similar to H. fasciata and H. diadema in having deep pronotal foveae PF2 and a very distinctive pronotal fascia ( Figs. 90 , 91 , 94 ); distinguished from H. fasciata by the slightly smaller size (ca. 1.47 vs. 1.55 mm), the more transverse pronotum (PL/PW ca. 0.77 vs. 0.86), and the slightly different plaque configurations; differentiated from H. diadema by the shorter and more widely spread plaques and the narrower elytra. Males are additionally differentiated by the more markedly modified protibiae of H. fasciata , and the more distinctly arcuate metatibiae of H. paxillipes . The male genitalia of the three species markedly differ ( Figs. 92, 93, 96). The metaventrite and the complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 319–321 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.47/0.63; head 0.22/0.33; pronotum 0.33/0.43, PA 0.37, PB 0.37; elytra 0.90/0.63. Dorsum of head piceous; pronotum testaceous in front of and behind piceous fascia, ratios of color bands, as measured in midline, ca. 7/11/5; elytra brown, with lighter, diffusely margined macula around summit of posterior declivity; legs light brown to testaceous; maxillary palpi testaceous.

Frons punctures ca. 1xef; interstices shining, 1–3xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum and postmentum very sparsely and very finely punctulate, strongly shining. Genae raised, shining, without posterior ridge. Pronotum cordiform, anterior margin very slightly emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 2–4xpd, punctures larger and denser at anterior and posterior; PF1 united to form shallow transverse impression across anterior 1/3 of pronotal disc; PF2 deep, oval, oblique, shallowly confluent; PF3 moderately deep; PF4 shallow.

Elytra with summit of posterior declivity slightly before midlength; lateral explanate margins narrow; on basal 1/3 punctures slightly smaller than largest pronotal punctures, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 1–3xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming moderate angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/1/4/5. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward apex. Plaques short, carinate, located at sides of deep, inverted V-shaped median depression. Metaventrite with very short midlongitudinal ridge anterior to apex of median depression, ridge not attaining mesoventral intercoxal process. AIS slightly concave, width at straight posterior margin ca. 1.5x P2. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia slightly thickened, medial margin bearing row of short stout peg-like spines. Mesotibia straight. Metatibia very slender, moderately arcuate, slightly thickened in distal 1/2. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 93).

Etymology. "Peg leg"; named in reference to the row of peg-shaped spines on the male protibiae.

Distribution. Currently known from Areas 2 and 3; elevation range 20–1100 m ( Fig. 472 ).

Figures

FIGURE 90. Hydraena fasciata, holotype, dorsal and lateral habitus, and venter.

FIGURE 91. Hydraena paxillipes, holotype, dorsal and lateral habitus, and venter.

FIGURE 94. Hydraena diadema, holotype, dorsal and lateral habitus, and venter.

FIGURES 316–321. Scanning electron micrographs of H. colorata (316–317) and H. paxillipes (318–321).

FIGURES 471–474. Geographical distributions of Hydraena species.