Hydraena ambripes, 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 : 21-22

Hydraena ambripes , new species

( Figs. 11 , 13 , 274–279 , 433 )

Type Material. Holotype (male): Madang Province: Finisterre Mts., Naho River Valley, Budemu , ex gravel banks of large river, 1264 m, 5° 56' S, 146° 40' E, 18 x 1964, M. E. Bacchus (MEB 61) ( NHM) . Paratypes (14): Eastern Highlands Province: Okapa , on logs and vegetable debris in small river, 1524 m, 6° 32' S, 145° 37' E, 10 ii 1965, M. E. Bacchus (MEB 187a) (3 NHM) ; Gulf Province: Marawaka, Mala , 1400 m, 7° 5.664' S, 145° 44.467' E, 11 xi 2006, Balke & Kinibel ( PNG 90) (5 MCZ, NHM, NMW, PNG, ZSM) ; Madang Province: Same data as holotype (4 NHM) ; Sandaun Province: Sokamin , ex leaves and rotting wood in stream, 1200 m, 4° 51.883' S, 141° 37.534' E, 20 x 2003, K. Sagata (WB 13) (2 ZSM) .

Differential diagnosis. Quite similar in dorsal habitus to H. ambra and H. sagatai ( Figs. 10 , 11 , 15 ); differing from H. ambra by the non-confluent pronotal foveae PF2, the differently shaped pronotum (PA and PB equal), the shorter elytra, and the smaller size (ca. 1.76 vs. 1.82 mm); differing from H. sagatai by the more strongly punctate pronotum, the median concavity of the first sternite, and the larger size (ca. 1.76 vs. 1.65 mm); males of H. ambripes are distinguished from males of both compared species by the markedly modified protibiae. The aedeagus of H. ambripes is most similar to that of H. ambra , but the two consistently differ in significant details ( Figs. 12, 13 ). The metaventrite and very complicated leg chaetotaxy are illustrated with SEMs ( Figs. 274–279 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.76/0.74; head 0.30/0.33; pronotum 0.41/0.51, PA 0.39, PB 0.38; elytra 1.07/0.74. Dorsum amber colored, head bicolored, frons darker than clypeus and labrum, legs light brown, maxillary palpi testaceous.

Frons punctures ca. 1xef; interstices shining, 1–3xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum very sparsely very finely punctate, shining; postmentum very finely densely micropunctulate in median concavity, surrounding areas smooth, shining. Genae raised, shining, without posterior ridge. Pronotum cordiform, anterior margin emarginate; lateral margins turning outward very slightly, if at all, at posterior angles; punctures on disc ca. 1xpd those of frons, interstices shining, 1–3xpd, punctures larger and denser at anterior; PF1 united to form shallow transverse impression across anterior 1/3 of pronotal disc; PF2 moderately deep, oval, not confluent in middle; PF3 and PF4 moderately deep.

Elytra distinctively humped just behind midlength, at summit of posterior declivity; lateral margins evenly arcuate; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, a few random, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 2xpd, as are interstices between punctures of a row. Apices in dorsal aspect very 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. 4/1.5/6/5. P1 narrow, not laminate; median carina sinuate in profile. P2 raised, l/w ca. as 3/2, sides slightly converging toward apex, apex joined to raised mesoventral intercoxal process. Plaques narrow, slightly arcuate, slightly converging toward one another anteriorly, weakly raised, weakly carinate laterally, located at sides of deep, median depression. Metaventrite with short midlongitudinal ridge between mesoventral intercoxal process and median depression, also with longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS and adjacent area on first ventrite conjointly forming shallow concavity; AIS width at straight posterior margin ca. 1.5x P2. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia markedly excavate on medial margin in distal 1/2. Mesotibia much narrower in distal 1/5 than at midlength. Metatibia gradually thickened from base to about distal 3/4, then markedly narrowed. Abdominal apex symmetrical.

Etymology. Named in reference to the amber color and sexually dimorphic legs.

Distribution. Currently known from four localities, three in Area 1 (at both the west and east ends) and one in Area 5; elevation range 1200–1524 m ( Fig. 433 ). This is one of ten species with distributions exclusively shared between Areas 1 and 5 ( Fig. 422 ).

Figures

FIGURE 10. Hydraena ambra, holotype, dorsal and lateral habitus, and venter.

FIGURE 11. Hydraena ambripes, holotype, dorsal and lateral habitus, and venter.

FIGURE 15. Hydraena sagatai, holotype, dorsal and lateral habitus, and venter.

FIGURES 12–13. Aedeagi of holotypes. 12. H. ambra. 13. H. ambripes.

FIGURES 274–279. Scanning electron micrographs of H. ambriceps.

FIGURES 431–434. Geographical distributions of Hydraena species.

FIGURES 421–422. 421. All known collecting localities for Papua New Guinea Hydraena. 422. Ten species, representing eight species groups, with distributions exclusively shared between Areas of Endemism 1 and 5.