Hydraena foliobba, 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 : 40-41

Hydraena foliobba , new species

( Figs. 50 , 52 , 292–295 , 393, 437 )

Type Material. Holotype (male): Morobe Province: Herzog Mts., Vagau [Wagau], ex gravel banks of slow-running river, elev. 1220 m, 6° 48' S, 146° 48' E, 11 i 1965, M. E. Bacchus (MEB 148b) ( NHM) . Paratypes (157): Central Province: Kokoda , under stones, river side, elev. 365 m, 8° 39' S, 147° 15' E, 1–30 viii 1933, L. E. Cheesman (577) (22 NHM) ; Eastern Highlands Province: Akameku–Brahmin , Bismarck Range, elev. 800 m, 5° 50.021' S, 145° 24.664' E, 24 xi 2006, Balke & Kinibel ( PNG 112) (6 MCZ, NHM, NMW, PNG, ZSM) ; Frigano , Mt. Michael, in bush stream, elev. [est.] 1600–1700 m, 6° 25' S, 145° 20' E, 1–30 vii 1975, R. W. Hornabrook (17 NMNZ) ; NE Kassam, 48 km E of Kainantu , elev. 1350 m, 6° 13' S, 146° 0' E, 1–30 x 1959, T. C. Maa (10 NHM) ; Gulf Province: Marawaka , near Ande, elev. 1000 m, 7° 3.598' S, 145° 44.375' E, 10 xi 2006, Balke & Kinibel ( PNG 89) (2 ZSM) ; Madang Province: Akameku–Brahmin , Bismarck Range, elev. 750 m, 5° 49.307' S, 145° 24.389' E, 25 xi 2006, Balke & Kinibel ( PNG 114) (19 MCZ, NHM, NMW, PNG, ZSM) ; Morobe Province: Herzog Mts. , Vagau [Wagau], ex gravel banks of slow-running river, elev. 1220 m, 6° 48' S, 146° 48' E, 4–17 i 1965, M. E. Bacchus (MEB 148b) (8 NHM) ; Herzog Mts. , Vagau [Wagau], 11 i 1965, M. E. Bacchus (MEB 148b) (5 NHM) ; Herzog Mts. , Vagau [Wagau], ex gravel banks of small clear river in dense forest, elev. 1220 m, 6° 48' S, 146° 48' E, 6 i 1965, M. E. Bacchus (MEB 140a) (6 NHM) ; Herzog Mts. , Vagau [Wagau], ex gravel banks of swift shallow clear river, elev. 1128 m, 6° 48' S, 146° 48' E, 4–17 i 1965, M. E. Bacchus (MEB 145a) (41 NHM) ; Herzog Mts. , Vagau [Wagau], 8 i 1965, M. E. Bacchus (MEB 145a) (2 NHM) ; Herzog Mts. , Vagau [Wagau], ex muddy gravel banks of shallow clear swift river, elev. 1220 m, 6° 48' S, 146° 48' E, 9 i 1965, M. E. Bacchus (MEB 147b) (3 NHM) ; Herzog Mts. , Vagau [Wagau], Snake River, under gravel in bed of large slow river, elev. 1220 m, 6° 48' S, 146° 48' E, 15 i 1965, M. E. Bacchus (MEB 152) (1 NHM) ; Wagau , Herzog Mts., elev. 1150 m, 6° 51.067' S, 146° 48.068' E, 19 xi 2006, Balke & Kinibel ( PNG 102) (15 MCZ, NHM, NMW, PNG, ZSM) .

Differential Diagnosis. Differentiated from the two other members of the Foliobba group by the "narrowwaisted" body form (TL/PB ca. 4.89 vs. 3.25 and 3.16), and the larger size (ca. 1.76 vs. 1.58 and 1.43 mm) ( Figs. 50 , 51 , 54 ). Hydraena foliobba additionally differs from H. striolata and H. infoveola by having the metaventral plaques slightly larger, the mesotibiae straight instead of arcuate, and the male metatibiae shaped differently. The aedeagus very distinctly differs from that of the compared species ( Figs. 52, 53 , 56 ). The metaventrite, and the very complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 292–295 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.76/0.69; head 0.28/0.39; pronotum 0.40/0.48, PA 0.42, PB 0.41; elytra 1.08/0.69. Dorsum of head piceous; pronotum testaceous in front of and very narrowly behind piceous fascia, ratios of color bands, as measured in midline, ca. 7/17/3; elytra dark brown; legs and maxillary palpi brown.

Frons punctures ca. 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 slightly larger than 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 slightly 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. 4/2/9/5. 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, with moderately long spine on medial surface at ca. distal 2/3. Mesotibia straight. Metatibia slightly emarginate on medial surface, except very slightly increased in width in apical 1/6 and here bearing row of short spines. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus ( Fig. 52 ) distal piece with sharply pointed, slightly arcuate process on left side, and large, leaf-shaped process apically. Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 393).

Etymology. "Leaf decanter"; named in reference to the leaf-shaped apical process of the aedeagus.

Distribution. With a moderately wide distribution, known from Areas 1 (eastern), 2, 6 and 7; elevation range 65–1700 m ( Fig. 437 ).

Figures

FIGURE 50. Hydraena foliobba, holotype, dorsal and lateral habitus, and venter.

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 292–297. Scanning electron micrographs of H. foliobba (292–295) and H. phainops (296–297).

FIGURES 435–438. Geographical distributions of Hydraena species.

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