Enithares orsaki, Polhemus, 2020

Polhemus, Dan A., 2020, Nine new species of Enithares (Heteroptera: Notonectidae) from New Guinea, with distributional notes on other species and an updated world checklist, Zootaxa 4772 (1), pp. 132-182 : 138-139

Enithares orsaki , sp. nov.

( Figs. 6 , 9, 10 , 16 , 22 )

Type material examined. Holotype, male (dissected), PAPUA NEW GUINEA, Madang Prov., rocky stream at Kau Wildlife Area, nr. Baitabag village, N. of Madang , 20 m., [vic. 5°08′46′′S, 145°46′15′′E], 26 March 1994, water temp. 28° C., 16:00–17:30 hrs., CL 7034, D. A. Polhemus ( BPBM) . Paratypes: 1 male, 3 females, same data as holotype, CL 7034, D. A . Polhemus ( BPBM) ; 1 male, 4 females, trib. to Mangen River at Reinduk, on Sevan road, 11 km. SW of Bunabun, 150 m ., [4°39′00′′S, 145°27′38′′E], 28 March 1994, water temp. 26° C., 11:00–14:00 hrs., CL 7036, D. A . Polhemus ( BPBM) . Additional specimens examined (not paratypes): 1 female, Gum River nr. Ohu, 11 km. W. of Madang, 80 m., [vic. 5°12′51′′S, 145°40′44′′E], 27 March 1994, water temp. 28° C., 10:00–14:00 hrs., CL 7035, D. A . Polhemus ( BPBM) .

Description. Male: Length 9.40 mm, width across pronotum 3.70 mm.

Coloration: Ground color yellowish-brown, with hemelytra darker greyish-brown ( Fig 9 ). Vertex and frons varying from uniform yellowish-brown, with a small roughly circular darker brown patch above base of labrum. Pronotum yellowish-brown, posterior margin slightly darker. Scutellum yellowish-brown. Hemelytra greyish-brown, often with with anterior margins of clavus bordering scutellum broadly yellowish-brown, forming a chevron-shaped fascia; wing membrane dark fumate brown. Legs brown, anterior edges of fore and hind femora margined with black; ventral surfaces of fore trochanters, middle and hind trochanters and femora marked with dark reddish brown. Venter brown.

Structural characters: Head broadly rounded anteriorly when viewed dorsally. Head length 1.00; greatest width 2.85, equal to 0.77 pronotal width; anterior width of vertex 1.00, equal to head length. Synthlipsis 0.50, about 0.50 anterior width of vertex and clearly shorter than pronotum. Pronotal length along midline 1.20, humeral width 3.70, lateral margins convex, posterior margin weakly sinuate. Dorsal margin of pronotal fovea directed caudad behind eyes ( Fig. 9 ). Nodal furrow nearly straight, removed by 2.0× its length from membranal suture, length 0.50, distance to membranal suture 1.00.

Front and hind legs typical for genus, lacking unusual modifications. Middle trochanter rounded. Middle femur with single moderately large, elongate, sharp subapical tooth, bordered basally by about 20 small black pegs, distally by about 3 similar pegs. Lengths of leg segments as follows: fore femur–tibia–tarsal 1–tarsal 2 = 1.40/1.80/0.60/0.30; middle femur–tibia–tarsal 1–tarsal 2 = 2.40/2.20/0.70/0.40; hind femur–tibia–tarsal 1–tarsal 2 = 3.50/3.10/1.40/0.80.

Ventral abdomen with metaxyphus triangular, slightly concave, tip acuminate ( Fig. 6 ).

Male genitalia when viewed laterally ( Fig. 16 ) with proctiger angular, apex acute; posterior lobe of pygophore with posteroventral angle obtuse, bearing a prominent tapering setal tuft, posterior lobe of pygophore erect, apex broad and blunt, posteriorly setiferous, slightly notched anteriorly on dorsal margin; paramere elongate, slightly tapering and curved anteriorly, apex rounded, reaching slightly above dorsal margin of posterior lobe; lateral arm of basal plate stout, elongate, gently curving, apex slightly expanded, truncate; aedeagus semicircular, with numerous transverse folds.

Female. Length 9.40, width across pronotum 3.70 mm. Similar to male in general structure and coloration ( Fig. 10 ).

Etymology. The name “orsaki” honors the late Dr. Larry Orsak, formerly of the Christensen Research Institute in Madang, and subsequently affiliated with the Papua New Guinea University of Technology in Lae. Larry was a tireless advocate for conservation of Papua New Guinea’s biodiversity, and the education of its younger generations so that they could provide informed stewardship of it into the future. He was also a good friend and will be missed.

Discussion. Enithares orsaki is similar to E. atra , with which it was confused by Lansbury (1968) —see the previous discussion under that species. The angular shape of the male proctiger is very similar in both species when viewed laterally, as is the general shape of the PL, with its broadly rounded apex and anterodorsal notch (compare Figs. 16, 17 ). The posteroventral angle of the pygophore is more pronounced in E. atra , however, while the apex of the paramere is more rounded in E. orsaki (compare Figs. 16, 17 ). The male paramere in E. orsaki is also curved very slightly anterad, whereas the anterior paramere margin is straight in E. atra . The major differences between these species lie in the structure of the LABP, which is gently sinuate and tapering in E. atra , coming to a slender apex, versus broadly curved and stout in E. orsaki , terminating in a slightly expanded and broadly truncate apex (compare Figs. 16, 17 ).

Ecological notes. The type locality at the Kau Wildlife Area (CL 7034), north of Madang, was a small, clear stream emerging from low hills behind the coast. The bed profile consisted of small, sloping cascades over bedrock sills, interspersed with long pools and shallow runs. The channel was heavily shaded when the collections were made late in the day. Enithares orsaki was found here in standing side pools amid the bedrock sills, free of fish and not directly connected to the main stream.

Additional specimens were taken along a tributary to the Mangan River at Reinduk (CL 7036), a village in the foothills of the Adelbert Mountains to the west of Madang. This small streamlet emerged from primary rain forest flowing over scattered exposures of travertine which formed small, dripping waterfalls, interspersed with shallow flowing riffles and small pools. Enithares orsaki was taken from the deeper pools along this tributary.

As currently understood, E. orsaki is confined to the northern coastal ranges of Papua New Guinea, with a distribution extending from the Adelbert Mountains in the vicinity of Madang eastward through the Huon Peninsula ( Fig. 22 ). The records of E. atra from Lae and Finschhafen listed by Lansbury (1968) are now considered to apply to this species instead. As such, E. orsaki occupies the Adelbert, Finisterre and Saruwaged Mountains area of freshwater endemism (Area 14) as defined by D. Polhemus & Allen (2007).

Figures

FIGURE 22. Distribution of species in the E. atra group on New Guinea. Circles = E. orsaki n. sp., triangles = E. papua n. sp.; squares = E. atra Brooks.

FIGURES 2–7. Enithares species, metaxiphus. 2. E. arfak n. sp.; specimen from Indonesia, West Papua Prov., Mupi River, CL 2646. 3. E. bosavi n. sp.; holotype specimen from Papua New Guinea, Southern Highlands Prov., Mt. Bosavi, CL 7206. 4. E. insularis n. sp.; specimen from Papua New Guinea, Milne Bay Prov., Fergusson Island, CL 7181. 5. E. kasim n. sp.; specimen from Indonesia, West Papua Prov., Kasim, CL 2630. 6. E. orsaki n. sp.; specimen from Papua New Guinea, Madang Prov., Reinduk, CL 7036. 7. E. papua n. sp.; specimen from Papua New Guinea, Central Prov., Tekadu, CL 7157.

FIGURES 9–15. Enithares species in the E. atra group, dorsal habitus photographs. 9–10. Enithares orsaki n. sp., male and female; specimens from Papua New Guinea, Madang Prov., Reinduk, CL 7036. 11–12. Enithares atra Brooks, male and female; specimens from Papua New Guinea, Central Prov., Dorobisoro, CL 7260. 13–14. Enithares insularis n. sp., male and female; specimens from Papua New Guinea, Milne Bay Prov., Fergusson Island, CL 7181. 15. Enithares bosavi n. sp., holotype male; specimen from Papua New Guinea, Southern Highlands Prov., Mt. Bosavi, CL 7206.

FIGURES 16–21. Enithares species in the E. atra group, male genitalic complex, left lateral view. 16. Enithares orsaki n. sp.; specimen from Papua New Guinea, Madang Prov., Baitabag, CL 7034. 17. Enithares atra Brooks; specimen from Papua New Guinea, Central Prov., Dorobisoro, CL 7264. 18. Enithares insularis n. sp.; specimen from Papua New Guinea, Milne Bay Prov., Fergusson Island, CL 7181. 19. Enithares bosavi n. sp., holotype; specimen from Papua New Guinea, Southern Highlands Prov., Mt. Bosavi, CL 7206. 20. Enithares papua n. sp.; specimen from Papua New Guinea, Central Prov., Tekadu, CL 7157. 21. Enithares peninsularis n. sp.; specimen from Papua New Guinea, Central Prov., Woitape, CL 7248.