Hydraena tholasoris, 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 : 135-136

Hydraena tholasoris , new species

( Figs. 250 , 252, 547 )

Type Material. Holotype (male): Morobe Province: Markham Valley, Gusap , c. 90 miles NW of Lae, large pond, muddy bottom with thick layer of dead leaves, dense Ceratophyllum , 305 m, 5° 59' S, 146° 5' E, 27–30 i 1965, M. E. Bacchus (MEB 162) ( NHM).

Differential Diagnosis. Among members of the Fundextra group, similar to H. fundextra in comparatively large size (ca. 1.50 and 1.54 respectively) and in dorsal sculpture ( Figs. 242 , 250 ). Hydraena tholasoris has a pronotal fascia whereas H. fundextra has a macula. The plaque ratios differ in the two species, with H. tholasoris having shorter and less widely separated plaques compared with P2 (ratios ca. 5/1/7/6 vs. 4/1/8/7); in addition, the plaques are anteriorly convergent in H. tholasoris and parallel in H. fundextra . The male genitalia of H. tholasoris distinctively differ from those of other members of the group ( Fig. 252).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.50/0.67; head 0.24/0.37; pronotum 0.39/0.53, PA 0.41, PB 0.53; elytra 0.88/0.67. Dorsum of head dark brown; pronotum testaceous in front of and behind diffusely margined, piceous fascia, ratios of color bands, as measured in midline, ca. 6/15/5; elytra brown; legs light brown; maxillary palpi testaceous, tip not darker. Dorsum very weakly shining.

Frons punctures ca. 1–2xef, slightly smaller and sparser medially; interstices effacedly microreticulate, dull, 0.5–2xpd. Clypeus effacedly microreticulate, very finely sparsely punctulate medially. Mentum very sparsely very finely punctulate, shining. Postmentum effacedly microreticulate in shallow median depression, otherwise finely sparsely punctate. Genae very slightly raised, shining, with shallow, obsolete median impression, without posterior ridge. Pronotum transverse, ca. median 3/4 of anterior margin slightly arcuate to posterior, sides arcuate, slightly emarginate between midlength and posterior angle; punctures on disc much larger than largest frons punctures, interstices strongly shining, ca. 1–3xpd, punctures anteriorly and posteriorly slightly larger than those on disc; PF1 and PF4 absent; PF2 very shallow; PF3 moderately deep, wide.

Elytra with posterior declivity very gradual, summit at or very near midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd of largest pronotal punctures, a few punctures subserial, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 1–2xpd, 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. 5/1/7/6. P1 slightly wider than laminate; median carina nearly straight in profile, very slightly arcuate between coxae. P2 markedly concave, length/width ca. 7/5, sides very slightly diverging toward blunt apex. Plaques narrow lines, very slightly raised posteriorly, tapering to points anteriorly, converging slightly anteriorly, at sides of densely punctate median depression. Metaventrite between mesocoxae slightly sloping, confluent with tip of P2. AIS width at straight posterior margin slightly greater than P2. All legs of moderate length. Profemur (male) without tubercle on ventral margin; protibia very slightly arcuate, gradually increasing in width from base to apex, posteromedial margin with small, low carina at about midlength. Meso- and metatibia straight, slender. Abdominal apex asymmetrical; last tergite (male) with deep concavity near apex, offset to left side. Aedeagus as illustrated ( Fig. 252).

Etymology. Judging from the male genitalia this species is the sister species of H. thola .

Distribution. Currently known only from the type locality, Markham Valley, Gusap, in the eastern arm of Area 3; elevation 305 m ( Fig. 547 ).

Figures

FIGURE 242. Hydraena fundextra, holotype, dorsal and lateral habitus, and venter.

FIGURE 250. Hydraena tholasoris, holotype, dorsal and lateral habitus, and venter.

FIGURES 547–550. Geographical distributions of Hydraena species.