Hydraena bifunda, 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 : 132-133

Hydraena bifunda , new species

( Figs. 243 , 245, 382–386 , 543 )

Type Material. Holotype (male): Morobe Province: c. 7 mi. Lae–Bulolo road, ex gravel and grass roots on bank of small stream, [GE est.] 10–30 m, 6° 41' S, 146° 54' E, 30 xii 1964, M. E. Bacchus (MEB 120) ( NHM) . Paratypes (52): Madang Province: 5 km N Kawe , plantation drain, [GE est.] 10–60 m, 4° 58' S, 145° 47' E, 11 iii 1991, D. Larson (2 MCZ) ; Gogal Valley , 4 km S Baru Village, [GE est.] 300–500 m, 5° 42' S, 146° 32' E, 10 iv 1991, D. Larson (2 MCZ) ; Ramu Valley , 2 km SE Brahman, [GE est.] 130–150 m, 5° 43' S, 145° 22' E, 18 iv 1991, D. Larson (1 MCZ) ; Ramu Valley , 4–5 km SW Yagumbu, [GE est.] 400–600 m, 5° 38' S, 145° 31' E, 15 iv 1991, D. Larson (3 MCZ) ; Ramu Valley , 6 km SW Yagumbu, [GE est.] 500–700 m, 5° 39' S, 145° 32' E, 15 iv 1991, D. Larson (3 MCZ) ; Morobe Province: Same data as holotype (6 NHM) ; c. 7 miles Lae – Bulolo road, ex gravel and grass roots on bank of small stream, [GE est.] 10–30 m, 6° 41' S, 146° 54' E, 30 xii 1964, M. E. Bacchus (MEB 120) (18 NHM) ; Huon Pen., road to Kwapsanek , 250 m, 6° 30.27' S, 146° 59.581' E, 31 iii 2006, Balke & Sagata ( PNG 24) (7 MCZ, NHM, NMW, PNG, ZSM) ; Lae, ex muddy gravel bank of small stream in Botanic Garden , [GE est.] 20–30 m, 6° 43' S, 147° 0' E, 12 xii 1964, M. E. Bacchus (MEB 118) (2 NHM) ; Markham Valley, Gusap , 90 miles NW of Lae, ex dead leaves on mud wetted by seepage, 305 m, 5° 59' S, 146° 5' E, 27–30 i 1965, M. E. Bacchus (MEB 163) (5 NHM) ; Markham Valley, Gusap , c. 90 miles NW of Lae, large pond, muddy bottom with thick layer of dead leaves, dense Ceratophyllum , 305 m, 5° 59' S, 146° 5' E, 27–30 i 1965, M. E. Bacchus (MEB 162) (3 NHM) .

Differential Diagnosis. Among members of the Fundextra group similar to H. thola in the plaque ratios, having P2 slightly wider than the plaque separation (ratios ca. 5/1/6/4 and 5/1/8/4 respectively) ( Figs. 243 , 247 ). Hydraena bifunda differs from H. thola and all other members of the Fundextra group in the degree to which the posterior part of P1 is raised. Hydraena bifunda differs dorsally from H. thola in the following characters: the frons is only weakly microreticulate, the pronotal punctures are only slightly larger than the frons punctures, the elytra have a few subserial discal punctures, and the pronotum has a fascia. The male genitalia of H. bifunda distinctively differ from those of other members of the group ( Fig. 245). The metaventrite and complicated leg chaetotaxy are illustrated with SEMs ( Figs. 382–386 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.33/0.60; head 0.22/0.33; pronotum 0.33/0.47, PA 0.37, PB 0.44; elytra 0.81/0.60. Dorsum of head dark brown; pronotum light brown to testaceous around brown, diffusely margined, fascia, ratios of color bands, as measured in midline, ca. 6/10/5; elytra brown; legs light brown; maxillary palpi testaceous, tip not darker. Dorsum weakly shining.

Frons punctures ca. 1xef, slightly smaller and sparser medially; interstices effacedly microreticulate, weakly shining, 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 punctulate. 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 ca. 1xpd of largest frons punctures, interstices strongly shining, ca. 2–3xpd, punctures 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 of largest pronotal punctures, a few punctures subserial, 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 conjointly rounded, in posterior aspect margins forming angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 5/1/6/4. P1 very slightly wider than laminate; in profile, median carina straight in front of coxae, behind coxae carina raised, arcuate in profile. P2 markedly concave, length/width ca. 6/5, sides parallel or very slightly converging toward blunt apex. Plaques carinate lines, converging slightly anteriorly, at sides of densely punctate median depression. Metaventrite between mesocoxae slightly sloping, confluent with tip of P2. AIS width at straight posterior margin ca. equal P2. All legs of moderate length. Profemur (male) with minute tubercle on ventral margin near basal 1/3; protibia very slightly arcuate, gradually increasing in width from base to apex, ventral margin with minute carina near 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. 245).

Etymology. Named in reference to the paired processes of the aedeagus, and to the relationship to H. funda .

Distribution. Currently known from the eastern parts of Areas 2 and 3, and both eastern and western parts of Area 5; elevation range 10–700 m ( Fig. 543 ).

Note. The holotype is slightly teneral; mature specimens have a darker pronotal fascia.

Figures

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

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

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

FIGURES 543–546. Geographical distributions of Hydraena species.