Hydraena sagatai, 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 : 23-24

Hydraena sagatai , new species

( Figs. 15 , 17 , 435 )

Type Material. Holotype (male): Sandaun Province: Abau River , ex plant debris, 1571 m, 4° 50.782' S, 141° 38.132' E, 13 x 2003, K. Sagata (WB 48) ( ZSM) . Paratypes (4): Sandaun Province: Same data as holotype (2 ZSM); May River , ex leaves and rotting wood in stream, 1718 m, 4° 49.779' S, 141° 38.174' E, 8 x 2003, K. Sagata (WB 46) (2 ZSM) .

Differential Diagnosis. Quite similar in dorsal habitus to H. ambripes and H. essentia ( Figs. 11 , 15 , 18 ); differing from H. ambripes by the confluent pronotal foveae PF2, the more finely punctate pronotum, and the smaller size (ca. 1.65 vs. 1.76 mm); differing from H. essentia by the more finely punctate pronotum, and the shallower pronotal foveae. Males of all three species have modified protibiae, those of H. sagatai being the least strongly modified. The aedeagus of H. sagatai is most similar to that of H. essentia , but the two consistently differ in significant details ( Figs. 17 , 20).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.65/0.68; head 0.27/0.34; pronotum 0.36/0.47, PA 0.35, PB 0.35; elytra 1.02/0.68. Dorsum amber colored, head bicolored, frons darker than clypeus and labrum, legs and maxillary palpi light brown.

Frons punctures ca. 1xef; interstices shining, 1–3xpd. Clypeus microreticulate laterally, very 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 slightly smaller and sparser than those of frons, interstices shining, 2–6xpd, punctures larger and denser at anterior ca. 1xpd; PF1 united to form very shallow transverse impression across anterior 1/3 of pronotal disc; PF2 moderately deep, oval, oblique, very shallowly confluent in middle, conjointly forming faint U-shaped impression; PF3 and PF4 moderately deep.

Elytra distinctively humped just behind 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. 2–4xpd, 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. Profemur (male) with moderately large, sharply pointed tubercle next to trochanter; protibia emarginate on medial surface in distal 1/2. Mesotibia simple. Metatibiae slender, very weakly emarginate on medial margin near midlength. Abdominal apex symmetrical.

Etymology. Named in honor of Papuan biologist Katayo Sagata, the collector of this and other new species of PNG Hydraena .

Distribution. Currently known only from two very narrowly separated localities in Saundaun Province: in the western extreme of Area 1; elevations 1571 m and 1718 m ( Fig. 435 ).

Figures

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

FIGURE 15. Hydraena sagatai, holotype, dorsal and lateral habitus, and venter.

FIGURE 18. Hydraena essentia, holotype, dorsal and lateral habitus, and venter.

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

FIGURES 435–438. Geographical distributions of Hydraena species.