Hydraena tricosipes, 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 : 51-52

Hydraena tricosipes , new species

( Figs. 70 , 72 , 310–313 , 460 )

Type Material. Holotype (male): Morobe Province: Herzog Mts., Vagau [Wagau], ex gravel banks of small clear river in dense forest, 1220 m, 6° 48' S, 146° 48' E, 6 i 1965, M. E. Bacchus (MEB 140a) ( NHM) . Paratypes (60): Gulf Province: Marawaka, near Ande , 1000 m, 7° 3.598' S, 145° 44.375' E, 10 xi 2006, Balke & Kinibel ( PNG 89) (1 ZSM) ; Madang Province: Finisterre Mts., Naho River Valley, Moro , 1691 m, 5° 50' S, 146° 7' E, 30 x–23 xi 1964, M. E. Bacchus (MEB 78) (8 NHM) ; Finisterre Mts., Naho River Valley, Moro , nr. Sewe , gravel bank of small stream running into River Naho , 1372 m, 5° 50' S, 146° 7' E, 2 xi 1964, M. E. Bacchus (MEB 81) (44 NHM) ; Finisterre Mts., Naho River Valley, nr. Moro , ex tiny puddles left in clay bottom of partly ephemeral pool, 1432 m, 5° 50' S, 146° 7' E, 7 xi 1964, M. E. Bacchus (MEB 92) (5 NHM) ; Morobe Province: Herzog Mts., Vagau [Wagau], ex gravel banks of small clear river in dense forest, 1220 m, 6° 48' S, 146° 48' E, 6 i 1965, M. E. Bacchus (MEB 140a) (2 NHM) .

Differential Diagnosis. Similar in habitus and some male sexual dimorphisms (no tubercle on first abdominal ventrite, fifth ventrite with transverse ridge, long hair-like setae on the meso- and metatarsi) to H. tarsotricha ( Figs. 67 , 70 ); differing therefrom by the smaller size (ca. 1.63 vs. 1.78 mm), and the narrower and shorter plaques (ratios ca. 3/3/11/1 vs. 3/4/13/1). The male genitalia of the two species also show a relationship, but differ in shapes of the main piece, distal piece, and parameres ( Figs. 69, 72 ). The metaventrite, antennal pocket, abdominal apex, and very complicated chaetotaxy of the protibiae are illustrated with SEMs ( Figs. 310–313 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.63/0.63; head 0.25/0.35; pronotum 0.38/0.44, PA 0.39, PB 0.38; elytra 0.98/0.63. Dorsum dark brown to piceous; pronotum slightly lighter along anterior margin, legs and maxillary palpi dark brown to brown.

Frons punctures ca. 1xef, slightly larger near eyes than medially; interstices shining, 1–5xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum very sparsely very finely punctulate, shining; postmentum densely micropunctulate, dull. 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, 2–4xpd, punctures larger and denser at anterior and posterior; PF1 absent; PF2 very shallow, obsolete; PF3 deep; PF4 absent.

Elytra with summit of posterior declivity slightly past midlength; lateral explanate margins 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. 2–3xpd, as are interstices between punctures of a row, some punctures on disc subserial. 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. 3/3/11/1. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward blunt apex. Plaques very large, very narrowly separated, slightly more narrowly separated posteriorly than anteriorly, weakly raised. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 1.7x P2. All legs long and very slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia straight or very slightly arcuate, distal 1/3 widened on anterior surface, moderately long spine on medial surface at base of widened area. Meso- and metatibia straight. Meso- and metatarsi with long hair-like setae along ventral margin. Fifth abdominal ventrite posteriorly very slightly transversely raised. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 72 ).

Etymology. "Tricky legs"; named in reference to the similarity of the male legs to other Tetana group members that have long hair-like setae on the meso- and metatarsi.

Distribution. Currently known from Areas 1, 5, and 6, with only one or two localities in each; elevation range 1000–1891 m ( Fig. 460 ).

Figures

FIGURE 67. Hydraena tarsotricha, holotype, dorsal and lateral habitus, and venter.

FIGURE 70. Hydraena tricosipes, holotype, dorsal and lateral habitus, and venter.

FIGURES 72–73. Aedeagi of holotypes. 72. H. tricosipes. 73. H. huonica.

FIGURES 310–315. Scanning electron micrographs of H. tricosipes (310–313) and H. tarsotricha (314–315).

FIGURES 459–462. Geographical distributions of Hydraena species.