Hydraena cavifrons, 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 : 104

Hydraena cavifrons , new species

( Figs. 179 , 181 , 517 )

Type Material. Holotype (male): Madang Province: Ramu Valley , 4.5 km N Brahman, [GE est.] 130–150 m, 5° 39' S, 145° 22' E, 18 iv 1991, D. Larson ( MCZ) . Paratypes (50): East Sepik Province: Sepik, main river, 20 m, 4° 12' S, 143° 36' E, 2 iii 1965, R. W. Hornabrook (5 NMNZ) ; Tambanum , main Sepik River , on flooded ground behind village, [GE est.] 5–20 m, 4° 12' S, 143° 36' E, 2 iii 1965, R. W. Hornabrook (17 NMNZ) ; Yentchan , main Sepik River , in small stream behind village, [GE est.] 20–50 m, 4° 8' S, 142° 55' E, 18 iii 1965, R. W. Hornabrook (14 NMNZ) ; Madang Province: Ramu Valley , 4.5 km N Brahman, [GE est.] 130–150 m, 5° 39' S, 145° 22' E, 18 iv 1991, D. Larson (10 MCZ) ; Ramu Valley, Brahman Mission stock pond, [GE est.] 130–150 m, 5° 43' S, 145° 22' E, 17 iv 1991, D. Larson (4 MCZ) .

Differential Diagnosis. Recognized from the two other members of the Luridipennis group in PNG by the concave frons and the comparative large metaventral plaques ( Fig. 179 ). Additionally differing from H. buloba by the differently shaped pronotum (PL/PW ca. 0.72 vs. 0.50), the less robust body, and the non-striate-impressed elytral series. The pro- and metatibiae of males differ in all three species, and the male genitalia distinctively differ ( Figs. 180, 181 , 184 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.19/0.88; head 0.36/0.46; pronotum 0.50/0.69, PA 0.51, PB 0.58; elytra 1.35/0.88. Dorsum of head and pronotal disc piceous, remainder of dorsum brown to dark brown; legs brown; maxillary palpi light brown to testaceous.

Frons concave near eyes, punctures ca. 1–2xef; interstices shining, 1–3xpd. Clypeus laterally subrugulose, medially less coarsely punctate. Mentum anteriorly shining, moderately coarsely punctate, posteriorly slightly concave, rugulose, dull; postmentum coarsely punctate, interstices weakly shining. Genae raised, lacking posterior ridge, midlongitudinally with small fovea in front of and behind ridge.

Pronotum densely coarsely punctate, punctures on disc deep, ca. 3–4xpd those of frons, interstices narrow walls to 1xpd; PF1 shallow, in midline extended to ca. midlength of pronotum; PF2 deep, oval, oblique; PF3 and PF4 deep, confluent.

Elytral punctures not striate-impressed, ca. 1xpd of largest pronotal punctures. Intervals shining, width ca. 1– 2xpd, interstices between punctures of a row less; third interval slightly raised, other intervals not raised. Explanate margin wide. Apices in dorsal aspect separately rounded, in posterior aspect margins forming angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/4/2.5. P1 laminate; median carina angulate in profile. P2 very narrow, l/w ca. 7/2, sides parallel, apex blunt.

Metaventral disc densely punctate beneath hydrofuge pubescence, plaques moderately large, widest posteriorly, tapering to point anteriorly, located basolaterally on sides of deep, inverted V-shaped median depression. Very short and low midlongitudinal ridge behind mesoventral intercoxal process. AIS flat, or nearly so, width at slightly arcuate posterior margin slightly greater than 3x P2. Abdominal apex asymmetrical, with short setae; last tergite notched on ventral face. Profemur with moderately large, sharply pointed tubercle on anterior margin near trochanter. Protrochanter very weakly keeled. Protibia slightly arcuate, distal 2/5 widened and forming ridge on medial margin, small tooth at base of ridge, same area with row of short, stout setae on ventral surface. Mesotibia straight. Metafemur with short, sparse setae on entire length of lower surface. Metatibia weakly arcuate, slender, dorsomedian margin with brush of sparse setae in distal 4/5. Aedeagus as illustrated ( Fig. 181 ).

Etymology. Named in reference to the concave frons.

Distribution. A lowland species, with localities in both the western and eastern parts of Area 3; elevation range 20–150 m ( Fig. 517 ).

Figures

FIGURE 179. Hydraena cavifrons, holotype, dorsal and lateral habitus, and venter.

FIGURES 180–181. Aedeagi. 180. H. impercepta, non-type specimen from Moitaka, 7 mi. N. of Port Moresby. 181. H. cavifrons, holotype.

FIGURES 515–518. Geographical distributions of Hydraena species.

FIGURES 184–185. Aedeagi of holotypes. 184. H. buloba. 185. H. impala.