Hydraena thola, 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 : 134-135

Hydraena thola , new species

( Figs. 247 , 249, 380–381 , 387 , 548 )

Type Material. Holotype (male): Central Province: Port Moresby – Brown River road, ex small pool in dry gravelly stream bed, [GE est.] 50–100 m, 9° 24' S, 147° 14' E, 15 iii 1965, M. E. Bacchus (MEB 196) ( NHM) . Paratypes (12): Central Province: Loloki , 10 miles N of Port Moresby, ex swamp, much grass, [GE est.] 30–50 m, 9° 20' S, 147° 10' E, 19 iii 1965, M. E. Bacchus (MEB 208) (2 NHM) ; Moitaka , 7 miles N of Port Moresby, ex dead leaves in gravelly shallow of small pond, [GE est.] 30–50 m, 9° 25' S, 147° 12' E, 17 iii 1965, M. E. Bacchus (MEB 207) (2 NHM) ; Port Moresby – Brown River road, ex grassy shallows of large muddy pond, [GE est.] 50–100 m, 9° 24' S, 147° 14' E, 15 iii 1965, M. E. Bacchus (MEB 195) (2 NHM) ; Port Moresby – Brown River road, ex small pool in dry gravelly stream bed, [GE est.] 50–100 m, 9° 24' S, 147° 14' E, 15 iii 1965, M. E. Bacchus (MEB 196) (6 NHM) .

Differential Diagnosis. Among members of the Fundextra group, similar to H. bifunda in the plaque ratios, having P2 slightly wider than the plaque separation (ratios ca. 5/1/8/4 and 5/1/6/4 respectively). Hydraena thola differs dorsally from H. bifunda in the following characters: the frons is strongly microreticulate, the pronotal punctures are much larger than the frons punctures, the elytral discal punctures are subserial or random, and the pronotum has a macula ( Figs. 243 , 247 ). In addition, the plaques are carinate only at the posterior extreme. The male genitalia of H. thola distinctively differs from those of other members of the group ( Fig. 249). The prosternum, meso- and metaventrites, and the complicated leg chaetotaxy of the male protibia are illustrated with SEMs ( Figs. 380–381 , 387 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.42/0.65; head 0.21/0.36; pronotum 0.37/0.52, PA 0.40, PB 0.52; elytra 0.88/0.65. Dorsum of head with posterior 1/2 of frons dark brown, remainder of frons, clypeus, and labrum light brown to testaceous; pronotum testaceous around light brown, diffusely margined, rectangular macula, ratios of color bands, as measured in midline, ca. 7/12/6; elytra brown; legs light brown; maxillary palpi testaceous, tip not darker. Dorsum weakly shining.

Frons punctures ca. 1xef, not notably smaller or 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. 0.5–2xpd, punctures anteriorly and posteriorly slightly larger than those on disc; PF1 and PF4 absent; PF2 very shallow, completely shallowly confluent in midline to form U-shaped impression; 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 largest pronotal punctures, punctures subserial or random, punctures becoming gradually smaller toward posterior. Interstices not raised, weakly shining, on disc ca. 1–2xpd. Apices in dorsal aspect weakly separately rounded, in posterior aspect margins forming angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 5/1/8/4. P1 very slightly wider than laminate; median carina nearly straight in profile, very slightly arcuate between coxae. P2 markedly concave, length/width ca. 3/2, sides very slightly diverging toward blunt apex. Plaques very narrow lines, weakly carinate posteriorly, converging 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) with small tubercle on ventral margin near basal 1/3; protibia slightly arcuate, posteromedial margin widened to form narrow ridge 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. 249).

Etymology. Named in reference to the depression between the mesocoxae.

Distribution. Currently known only from a tight cluster of localities near Port Moresby, Area 11; elevation range ca. 30–100 m ( Fig. 548 ).

Figures

FIGURE 243. Hydraena bifunda, holotype, dorsal and lateral habitus, and venter.

FIGURE 247. Hydraena thola, holotype, dorsal and lateral habitus, and venter.

FIGURES 376–381. Scanning electron micrographs of H. receptiva (376–379) and H. thola (380–381).

FIGURES 382–387. Scanning electron micrographs of H. bifunda (382–386) and H. thola (387).

FIGURES 547–550. Geographical distributions of Hydraena species.