Hydraena spinobesa, 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 : 85

Hydraena spinobesa , new species

( Figs. 142 , 144 , 334–336 , 406 , 496 )

Type Material. Holotype (male): Madang Province: Finisterre Mts., Naho River Valley, Budemu , ex sand and gravel banks of small stream, but only in the 20 yards that it is permanent, 1264 m, 5° 56' S, 146° 40' E, 19 x 1964, M. E. Bacchus (MEB 62) ( NHM) . Paratypes (47): Eastern Highlands Province: Okapa , ex muddy gravel banks of fast, clear stream, 1524 m, 6° 32' S, 145° 37' E, 9 ii 1965, M. E. Bacchus (MEB 183) (10 NHM) ; Madang Province: Same data as holotype (4 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) (2 NHM) ; Finisterre Mts., Naho River Valley, nr. Moro , ex dead leaves and muddy gravel by small stream, 1372 m, 5° 50' S, 146° 7' E, 5 xi 1964, M. E. Bacchus (MEB 88) (10 NHM) ; Finisterre Mts., Naho River Valley, nr. Moro , ex gravel banks of small fast stream, 1432 m, 5° 50' S, 146° 7' E, 7 xi 1964, M. E. Bacchus (MEB 91) (10 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) (11 NHM) . The metaventrite, abdominal apex, and very complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 334–336 ) .

Differential Diagnosis. Similar in body proportions and size (ca. 1.28 vs. 1.23 mm) to H. saluta ( Figs. 142 , 147 ); differentiated therefrom by the more densely punctate pronotum, the narrower P2, and the narrower plaques (ratios ca. 1/1/4/4 vs. 2/1/3/1.5). The aedeagi of the two species distinctively differ ( Figs. 144 , 149 ). The metaventrite, abdominal apex, and very complicated chaetotaxy of the tibiae are illustrated with SEMs ( Figs. 334–336 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.28/0.56; head 0.21/0.33; pronotum 0.29/0.44, PA 0.38, PB 0.38; elytra 0.78/0.56. Dorsum dark brown to piceous; legs light brown; maxillary palpi light brown to testaceous, tip not darker.

Frons punctures ca. 1–2xef, larger and denser near eyes than medially; interstices effacedly microreticulate, dull or weakly shining, 1–3xpd. Clypeus microreticulate laterally, finely, moderately densely punctate medially. Mentum and postmentum very sparsely very finely punctulate, shining. Genae raised, shining, without posterior ridge. Pronotum transverse (PL/PW ca. 0.66), ca. median 3/5 of anterior margin very slightly arcuate to posterior; coarsely, densely punctate, punctures on disc ca. 3xpd frons punctures, interstices on disc shining, 1–2xpd, punctures slightly smaller and denser at anterior and posterior; sculpture laterally microreticulate and densely punctate, subrugulose; PF1 absent or very shallow, obsolete; PF2 shallow; PF3 shallow; PF4 absent.

Elytra with summit of posterior declivity slightly anterior to midlength; lateral explanate margins narrow; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, a few punctures subserial, punctures becoming gradually smaller toward posterior. Intervals not raised, weakly shining, on disc ca. 1xpd, 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. 1/1/4/4. P1 laminate; median carina sinuate in profile. P2 very narrow, raised slightly at tip, l/w ca. 5/1, sides slightly converging toward apex. Plaques very narrow, weakly raised, converging slightly anteriorly, at sides of median depression that continues shallowly to tip of P2. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 3xP2. All legs rather short, femora moderately robust. Profemur (male) without tubercle next to trochanter; protibia widest slightly past midlength, medial margin very slightly emarginate, lateral margin arcuate and bearing short stout spines in widest part. Mesotibia straight, lateral margin slightly arcuate and bearing contiguous row of short stout spines. Metatibia very weakly, if at all, arcuate, gradually increasing in width from base to apex, medial margin with few moderately long setae in distal 1/3, lateral margin with some short spines in distal 1/2. Abdominal apex symmetrical; last tergite (male) notched. Aedeagus as illustrated ( Fig. 144 ). Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 406 ).

Etymology. Named in reference to the spinose tibiae and to the wide body.

Distribution. Currently known from Okapa, in the eastern part of Area 1 (1524 m), and localities in the Finisterre Mts. of Area 5 (1264–1432 m)( Fig. 496 ). This is one of ten species with distributions exclusively shared between Areas 1 and 5 ( Fig. 422 ).

Figures

FIGURE 142. Hydraena spinobesa, holotype, dorsal and lateral habitus, and venter.

FIGURE 147. Hydraena saluta, holotype, dorsal and lateral habitus, and venter.

FIGURES 144–145. Aedeagi of holotypes. 144. H. spinobesa. 145. H. reticulobesa.

FIGURES 334–339. Scanning electron micrographs of H. spinobesa (334–336) and H. saluta (337–339).

FIGURES 404–407. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 495–498. Geographical distributions of Hydraena species.

FIGURES 148–149. Aedeagi of holotypes. 148. H. owenobesa. 149. H. saluta.

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.