Hydraena pacificica, 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 : 110

publication ID	https://doi.org/ 10.11646/zootaxa.2944.1.1
DOI	https://doi.org/10.5281/zenodo.5291728
persistent identifier	https://treatment.plazi.org/id/03B087E5-5B08-FFFE-FF79-F2BAFE1FF991
treatment provided by	Felipe
scientific name	Hydraena pacificica
status	sp. nov.

Treatment

Hydraena pacificica View in CoL , new species

( Figs. 194 View FIGURE 194 , 196 View FIGURES 196–197 , 521 View FIGURES 519–522 )

Type Material. Holotype (male): Morobe Province: Huon Peninsula , Kwapsanek, 850 m, 6° 34.913' S, 147°.526' E, 31 iii 2006, Balke & Sagata ( PNG 25) ( ZSM).

Differential Diagnosis. Similar in body proportions and dorsal sculpture to H. apertista ( Figs. 191 View FIGURE 191 , 194 View FIGURE 194 ). These two species have the mesoventral intercoxal process (P2) very short (length slightly less than the apical width), compared with the other species in the Impala group. Hydraena pacificica differs from H. apertista in the slightly more strongly emarginate anterior margin of the pronotum, the different plaque ratios (ca. 4/1/4/5 vs. 6/1/5/ 7), and in general a less uniform dorsal coloration, with an ill-defined pronotal macula. The general plan of the male genitalia of the two species also suggests a relationship, but the genitalia distinctively differ in details, and should be examined for reliable determinations ( Figs. 193 View FIGURES 192–193 , 196 View FIGURES 196–197 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.31/0.58; head 0.22/0.30; pronotum 0.31/0.44, PA 0.34, PB 0.36; elytra 0.77/0.58.

Dorsum of head with frons dark brown to dark reddish brown, clypeus lighter, brown, labrum testaceous; pronotum brown around ill-defined dark reddish brown macula on disc; elytra dark brown to dark reddish brown; legs reddish brown; maxillary palpi testaceous, tip not darker.

Frons punctures ca. 1–2xef, slightly larger near eyes than medially; interstices shining, 1–3xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum and postmentum very sparsely very finely punctulate, shining. Genae raised, shining, without posterior ridge. Pronotum subcordiform, ca. median 3/4 of anterior margin arcuate to posterior; punctures on disc ca. 1xpd frons punctures, interstices shining, 2–4xpd, punctures larger and denser at anterior and posterior; PF1 and PF2 very shallow, obsolete; PF3 moderately deep; PF4 absent or very shallow.

Elytra with summit of posterior declivity at or very near midlength; lateral explanate margins rather wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, a few punctures subserial, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 2–3xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/1/4/5. P1 ca. 1/2 P2; median carina bisinuate in profile. P2 very short, l/w ca. 3/4, sides slightly converging toward blunt apex. Plaques very narrow, carinate, converging very slightly anteriorly, at sides of deep median depression. Metaventrite concave between P2 and plaques. AIS width at straight posterior margin ca. 1.7x P2. All legs moderately long and slender. Profemur (male) with very small tubercle next to trochanter; protibia slightly arcuate, anterior margin very slightly widened subapically, medial margin flat except small sharp tubercle subapically on posteromedial margin. Meso- and metatibia straight. Abdominal apex symmetrical; last tergite (male) very deeply notched. Aedeagus as illustrated ( Fig. 196 View FIGURES 196–197 ).

Etymology. Named in reference to the shape of the distal process of the aedeagus, which recalls the two-fingered universal peace (or victory) sign.

Distribution. Currently known only from the type locality in the Huon Peninsula, in southeastern Area 5; elevation 850 m ( Fig. 521 View FIGURES 519–522 ).