Hydraena striolata, 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 : 41-42

Hydraena striolata , new species

( Figs. 51 , 53 , 514 )

Type Material. Holotype (male): Oro Province: Northern District, Tanbugal Afore village , elev. [est.] 300–500 m, 9° 7' S, 148° 23' E, 16 viii 1975, R. W. Hornabrook ( NMNZ) . Paratypes: Same data as holotype (7 NMNZ) .

Differential Diagnosis. Among members of the Foliobba group, most similar in dorsal habitus to H. infoveola ( Figs. 51 , 54 ); differing therefrom by the smaller size (ca. 1.43 vs. 1.58 mm), the brown color bands on each side of the pronotal fascia (testaceous in H. infoveola ), the slightly more impressed pronotal foveae PF2, and the more narrowly separated metaventral plaques. Males of the two species are additionally differentiated by differences in the shapes of the tibiae, and by the striolate area on the fifth abdominal ventrite of H. striolata ( Fig. 51 ). The aedeagi of the two species distinctively differ ( Figs. 53 , 56 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.43/0.58; head 0.25/0.34; pronotum 0.34/0.42, PA 0.36, PB 0.36; elytra 0.84/0.58. Dorsum of head piceous; pronotum light brown in front of and very narrowly behind piceous fascia, ratios of color bands, as measured in midline, ca. 6/14/3; elytra dark brown; legs and maxillary palpi brown to dark brown.

Frons punctures slightly larger than 1xef; interstices shining, 1–3xpd. 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 emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 1–3xpd, punctures slightly larger and denser at anterior and posterior; PF1 absent or obsolete; PF2 very shallow, obsolete; PF3 moderately deep; PF4 absent.

Elytra with summit of posterior declivity at or very near midlength; lateral explanate 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. 1–2xpd, as are interstices between punctures of a row. Apices in dorsal aspect weakly separately rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/2/7/3. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward apex. Plaques moderately wide, converging very slightly anteriorly, weakly raised, located at sides of deep, median depression. Metaventrite with short low ridge extended from each mesoventral coxal cavity. AIS width at straight posterior margin ca. 1.5x P2. All legs long and very slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia slightly arcuate, gradually increasing in width from base to apex. Mesotibia moderately arcuate, ca. to same degree as protibia. Metatibia straight. Fifth ventrite median area (male) striolate (with very fine, closely spaced, parallel impressed lines) ( Fig. 51 ). Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus ( Fig. 53 ) main piece with large, sharply pointed, markedly arcuate process on left side; distal piece large in both ventral and lateral views.

Etymology. Named in reference to the striolate area on the male fifth abdominal ventrite.

Distribution. Currently known only from the type locality, Tanbugal Afore village, in central Area 8, at or very near the border with Area 7; elevation 300–500 m ( Fig. 514 ).

Notes. The holotype has a very narrow groove across part of the occipital area of the head ( Fig. 51 ); this groove, apparently an anomaly, is not present on the other specimens examined.

Figures

FIGURE 51. Hydraena striolata, holotype, dorsal and lateral habitus, venter, and abdominal apex.

FIGURE 54. Hydraena infoveola, holotype, dorsal and lateral habitus, and venter.

FIGURES 52–53. Aedeagi of holotypes. 52. H. foliobba. 53. H. striolata.

FIGURES 511–514. Geographical distributions of Hydraena species.

FIGURES 56–57. Aedeagi of holotypes. 56. H. infoveola. 57. H. otiarca.