Hydraena apertista, 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 : 109

publication ID	https://doi.org/ 10.11646/zootaxa.2944.1.1
persistent identifier	https://treatment.plazi.org/id/03B087E5-5B09-FFFF-FF79-F041FD31F804
treatment provided by	Felipe
scientific name	Hydraena apertista
status	sp. nov.

Treatment

Hydraena apertista View in CoL , new species

( Figs. 191 View FIGURE 191 , 193 View FIGURES 192–193 , 520 View FIGURES 519–522 )

Type Material. Holotype (male): Madang Province: Finisterre Mts., Lower Naho Valley, Hinggia , ex rocks and gravel bank of swift clear stream, 762 m, 5° 50' S, 146° 7' E, 28 xi 1964, M. E. Bacchus (MEB 112) ( NHM). GoogleMaps

Differential Diagnosis. Similar in body proportions and dorsal sculpture to H. pacificica ( 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 apertista differs from H. pacificica in the slightly less emarginate anterior margin of the pronotum, the different plaque ratios (ca. 6/1/5/7 vs. 4/1/4/5), and in general a more uniform dorsal coloration. 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) 1.48/0.63; head 0.23/0.33; pronotum 0.33/0.47, PA 0.37, PB 0.38; elytra 0.88/0.63. Dorsum dark reddish brown, lateral areas of pronotum lighter than disc; legs brown to light 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 very sparsely very finely punctulate, shining; postmentum medially slightly concave and effacedly micropunctulate, otherwise finely sparsely punctate. 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, 1–3xpd, punctures slightly larger and denser at anterior and posterior; PF1 very shallow, obsolete; PF2 very shallow, obsolete; PF3 moderately deep; PF4 absent or very shallow.

Elytra with summit of posterior declivity slightly anterior to midlength; lateral explanate margins rather wide in anterior 1/2; 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. 4/1/5/7. P1 ca. 1/2 P2; median carina bisinuate in profile. P2 raised, very short, length slightly less than apical width, 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 small tubercle next to trochanter; protibia slightly arcuate, distal 1/3 widened anteriorly, medial margin flat except small sharp tubercle subapically on posteromedial margin. Meso- and metatibia straight. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 193 View FIGURES 192–193 ).

Etymology. "Opener"; named in reference to the bottle-opener shape of the aedeagal process.

Distribution. Currently known only from the type locality in the Finisterre Mts.; Area 5 but very near the bor- der with Area 3; elevation 762 m ( Fig. 521 View FIGURES 519–522 ).