Hydraena incisiva, 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 : 127-128

Hydraena incisiva , new species

( Figs. 234 , 236, 373–375 , 415 , 539 )

Type Material. Holotype (male): Morobe Province: Herzog Mts., Vagau [Wagau], small pools in clay rainwater gulley, 1524 m, 6° 48' S, 146° 48' E, 12 i 1965, M. E. Bacchus (MEB 150) ( NHM) . Paratypes (19): Eastern Highlands Province: Marawaka , Ande, 1700–1800 m, 7° 1.697' S, 145° 49.807' E, 9 xi 2006, Balke & Kinibel ( PNG 87) (5 ZSM) ; Okapa , large muddy pond, no vegetation, 1524 m, 6° 32' S, 145° 37' E, 10 ii 1965, M. E. Bacchus (MEB 185) (4 NHM) ; Morobe Province: ca. 10 km S Garaina Saureri , 1600 m, 7° 55' S, 147° 5' E, 24 iii 1998, A. Riedel (1 NMW) ; Herzog Mts. , Vagau [Wagau], small pools in clay rain-water gulley, 1524 m, 6° 48' S, 146° 48' E, 12 i 1965, M. E. Bacchus (MEB 150) (9 NHM) .

Differential Diagnosis. Differentiated from other members of the Incisiva group by the unicolored reddish brown dorsum (other species have a pronotal macula) ( Fig. 234 ). The metaventral plaques are slightly shorter (compared with their separation) than those of the other Incisiva group members (ratios ca. 5/2/6/5). The male hind tibiae are widest at midlength, similar to H. carinocisiva . The aedeagus is very distinctive and should be examined for reliable determinations ( Fig. 236). The prosternum, meso- and metaventrite, abdominal apex of female, and very complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 373–375 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.58/0.66; head 0.21/0.34; pronotum 0.39/0.53, PA 0.39, PB 0.50; elytra 0.96/0.66. Dorsum and legs reddish brown, frons slightly darker; maxillary palpi light reddish brown to testaceous, tip not darker. Dorsum shiny.

Frons punctures ca. 1–2xef near eyes, smaller and much sparser medially; interstices shining, 1–2xpd laterally, ca. 2–4xpd medially. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate medially. Mentum very sparsely very finely punctulate, shining. Postmentum microreticulate, moderately dull. Genae very slightly raised, shining, without posterior ridge. Pronotum subtrapezoidal, ca. median 3/4 of anterior margin slightly arcuate to posterior, sides slightly arcuate; punctures on disc ca. 1xpd of largest frons punctures, interstices strongly shining, ca. 1–3xpd; PF1, PF2 and PF4 absent; PF3 shallow.

Elytra with posterior declivity very gradual, summit at or very near midlength; lateral explanate margins moderately 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. 1–3xpd, 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. 5/2/6/5. P1 laminate; median carina nearly straight in profile, very slightly arcuate between coxae. P2 transversely concave, length ca. equal width, sides very slightly diverging toward blunt apex. Plaques roundly slightly raised, very slightly converging anteriorly, almost parallel, at sides of median depression. Metaventrite between mesocoxae slightly raised. AIS width at straight posterior margin slightly greater than P2. All legs of moderate length, tibiae very slender. Profemur (male) without tubercle next to trochanter; protibia straight, medial margin increasing in width from base to distal 1/4, then excavate to apex, few large spines at base of excavation, and contiguous row of very short spines along excavation. Mesotibia straight. Metatibia straight, narrow, but widest at midlength. Abdominal apex symmetrical, distinctly microreticulate; last tergite (male) with small apicomedian notch. Aedeagus as illustrated ( Fig. 236). Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 415 ).

Etymology. Named in reference to the relatively simple aedeagal contours and the slender blade-like process.

Distribution. Currently known from four localities, two in far eastern Area 1 (1524 m, and 1700–1800 m), and one each in Area 6 (Herzog Mts., 1524 m), and the northern part of Area 7 (1600 m) ( Fig. 539 ).

Figures

FIGURE 234. Hydraena incisiva, holotype, dorsal and lateral habitus, and venter.

FIGURES 370–375. Scanning electron micrographs of H. funda (370–372) and H. incisiva (373–375).

FIGURES 412–415. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 539–542. Geographical distributions of Hydraena species.