Hydraena pilulambra, 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 : 25

Hydraena pilulambra , new species

( Figs. 19 , 21, 436 )

Type Material. Holotype (male): Eastern Highlands Province: Clear stream, summit of Kassem Pass at forest level, 1450 m, 6° 18' S, 145° 52' E, 27 vii 1975, R. W. Hornabrook ( NMNZ) . Paratypes (54): Eastern Highlands Province: Akameku– Brahmin , Bismarck Range, 2400 m, 5° 55.615' S, 145° 22.699' E, 23 xi 2006, Balke & Kinibel ( PNG 107) (1 ZSM) ; Akameku– Brahmin , Bismarck Range ,, 2200 m, 5° 56.801' S, 145° 22.238' E, 23 xi 2006, Balke & Kinibel ( PNG 106) (8 MCZ, NHM, NMW, PNG, ZSM) ; Clear stream, summit of Kassem Pass at forest level, 1450 m, 6° 18' S, 145° 52' E, 27 vii 1975, R. W. Hornabrook (9 NMNZ) ; Western Highlands Province: Mondmill , 5 km SE Minj, small pools near creek, 1740 m, 5° 56.801' S, 144° 39.898' E, 12 vi 2006, John ( PNG 77) (5 NMNZ) ; Sepik River Basin , Waré Creek, partially shaded montane stream with angular, moss–covered boulders, small waterfalls and pools, 2000 m, 5° 42' S, 144° 39' E, 1 vii–30 viii 1988, D. Dudgeon (31 NMW) .

Differential Diagnosis. Similar to H. ambroides in size (ca. 1.71–1.74 mm), unicolored head, and males lacking distinctively modified legs; differing therefrom by the much more prominent dorsal setae, the slightly smaller eyes, the slightly smaller pronotum, and the more strongly arcuate elytral margins ( Figs. 11 , 19 ). The aedeagi of the two species distinctively differ ( Figs. 16 , 21).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.74/0.73; head 0.28/0.37; pronotum 0.38/0.47, PA 0.39, PB 0.39; elytra 1.05/0.73. Dorsum dark brown to piceous, head and disc of pronotum darkest, head not bicolored, legs and maxillary palpi brown.

Eyes comparatively small, rather coarsely faceted. Pronotum rather small compared with size of elytra. Dorsal setae prominent, especially on pronotum. Frons punctures ca. 1xef; interstices shining, 1–3xpd. Clypeus microreticulate laterally, finely sparsely punctate medially. Mentum very sparsely very finely punctate, shining; postmentum very finely densely micropunctulate in median concavity, surrounding areas smooth, shining. Genae raised, shining, without posterior ridge. Pronotum cordiform, anterior margin emarginate; lateral margins turning outward slightly at posterior angles; punctures on disc ca. 1xpd those of frons, interstices shining, 1–3xpd, punctures larger and denser at anterior and posterior; PF1 united to form transverse impression across anterior 1/3 of pronotal disc; PF2 deep, oval, oblique, very shallowly confluent in middle; PF3 and PF4 deep.

Elytra distinctively humped at midlength, at summit of posterior declivity; lateral margins evenly arcuate; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, a few random, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 1xpd, as are interstices between punctures of a row. Apices in dorsal aspect very weakly separately rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/2/7/5. P1 narrow, not laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward apex, apex joined to raised mesoventral intercoxal process. Plaques moderately narrow, slightly arcuate, converging toward one another anteriorly, weakly raised, located at sides of deep median depression. Metaventrite with very low and very short midlongitudinal ridge between mesoventral intercoxal process and median depression, also with short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS weakly concave, width at straight posterior margin ca. 2x P2. All femora very slender. Profemur (male) with moderately large, sharply pointed tubercle next to trochanter; protibia very slender, very slightly emarginate on medial surface. Meso- and metatibiae slender, widest at midlength. Abdominal apex symmetrical.

Etymology. Named in reference to the relatively (for the Ambra group) hairy dorsum, and relationship to H. ambra (pilula = hair; diminutive).

Distribution. Currently known only from Area 1 (eastern); elevation range 1450–2400 m ( Fig. 436 ).

Figures

FIGURE 11. Hydraena ambripes, holotype, dorsal and lateral habitus, and venter.

FIGURE 19. Hydraena pilulambra, holotype, dorsal and lateral habitus, and venter.

FIGURES 435–438. Geographical distributions of Hydraena species.

FIGURES 16–17. Aedeagi of holotypes. 16. H. ambroides. 17. H. sagatai.