Hydraena diadema, 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 : 62

Hydraena diadema , new species

( Figs. 94 , 96, 443 )

Type Material. Holotype (male): Eastern Highlands Province: Purosa Valley, nr. Okapa , on submerged stones, [GE est.] 1500–1700 m, 6° 32' S, 145° 37' E, 8 ii 1965, M. E. Bacchus (MEB 182a) ( NHM) . Paratypes: Morobe Province: Lae–Bulolo road, Patep Creek , ex gravel bank of large fast river, [GE est.] 900–1100 m, 6° 52' S, 146° 37' E, 28 xii 1964, M. E. Bacchus (MEB 126) (4 NHM) .

Differential Diagnosis. Among members of the Colorata group similar to H. fasciata and H. paxillipes in having deep pronotal foveae PF2 and a very distinctive pronotal fascia ( Figs. 90 , 91 , 94 ); distinguished from both species by the more ovoid elytra, the proportionally larger pronotal fascia, and the different plaque ratios. The male genitalia of the three species markedly differ ( Figs. 92, 93, 96).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.47/0.65; head 0.22/0.34; pronotum 0.36/0.43, PA 0.37, PB 0.36; elytra 0.88/0.65. Dorsum of head piceous; pronotum light brown to testaceous in front of and behind piceous fascia, ratios of color bands, as measured in midline, ca. 6/13/5; elytra dark brown; legs light brown; maxillary palpi testaceous, tip of palpus not darker.

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

Elytra very convex, widest slightly past midlength, apically broadly rounded; posterior declivity very steep, summit before midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 1–3xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect conjointly broadly rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/1/6/4. P1 laminate; median carina sinuate in profile. P2 raised in form of low keel, l/w ca. 2/1. Plaques very narrow, carinate, especially posteriorly, parallel, located at sides of deep, median depression. Metaventrite anteriorly with low midlongitudinal ridge. AIS at least partially fused with first abdominal ventrite, width at straight posterior margin ca. 1.5x P2. All legs moderately long and slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia very slightly arcuate, slightly wider subapically than apically. Mesotibia straight. Metatibia slightly arcuate. Abdominal apex symmetrical; last tergite (male) notched.

Etymology. "Headband"; named in reference to the testaceous band above the eyes, on the pronotum.

Distribution. Currently known from two localities, one in eastern Area 1 at 1500–1700 m, and one that is at the border of Areas 3 and 6, at 900–1100 m ( Fig. 443 ).

Figures

FIGURE 90. Hydraena fasciata, holotype, dorsal and lateral habitus, and venter.

FIGURE 91. Hydraena paxillipes, holotype, dorsal and lateral habitus, and venter.

FIGURE 94. Hydraena diadema, holotype, dorsal and lateral habitus, and venter.

FIGURES 443–446. Geographical distributions of Hydraena species.