Enithares tagula, 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 : 150-151

Enithares tagula new species

( Figs. 33, 34 , 38 , 55 )

Type material examined. Holotype, male (dissected): PAPUA NEW GUINEA, Milne Bay Prov., Louisiade Archipelago, Tagula [Sudest] Island , Kalitau Creek , 1 km. upstream from head of estuary, 0–30 m. [0–100 ft.], 11°21′52′′S, 153°14′26′′E, water temp. 24.4° C., 29 August 2002, 09:30–14:30 hrs., CL 7190, D. A. and J. T. Polhe- mus ( USNM) . Paratypes: 2 males, 1 female, 1 immature, same data as holotype, CL 7190, D. A . and J. T. Polhemus ( USNM, BPBM) ; 5 males, 2 females, Louisiade Archipelago, Tagula [Sudest] Island , small spring-fed stream near Kalitau Creek, 45 m . [150 ft.], water temp. 26° C., 29 August 2002, 10:00–12:00 hrs., 11°21′30′′S, 153°14′40′′E, CL 7192, D. A . and J. T. Polhemus ( USNM, BPBM) .

Description. Male: Length 8.90 mm, width across pronotum 3.40 mm.

Coloration: Ground color dark brown to black, with scattered pale brown markings on pronotum and hemelytra ( Fig. 33 ). Vertex and frons orange-brown, with an irregular dark brown patch at apex of head flanked by reddish; irregular dark brown, transverse, inverted V-shaped fascia present on lower frons, isolating a roughly triangular dark yellow patch above base of labrum. Pronotum yellowish-brown on anterior two-thirds between and surrounding pronotal fovea, greyish-brown along posterior margin. Scutellum dark brown to black, with central section embrowned. Hemelytra greyish-brown, with inner margins of clavus, outer base of clavus, outer and posterior corium with large, irregular tan patches; wing membrane black. Legs with coxae dark yellowish, all other segments medium brown, anterior faces of fore femora broadly suffused with black; ventral surfaces of trochanters and femora marked with dark reddish brown. Venter brown.

Structural characters: Head broadly rounded anteriorly when viewed dorsally. Head length 0.75; greatest width 2.75, equal to 0.81 pronotal width; anterior width of vertex 0.90, equal to 1.20 head length. Synthlipsis 0.60, about 0.67 anterior width of vertex and clearly shorter than pronotum. Pronotal length along midline 1.00, humeral width 3.40, lateral margins convex, posterior margin weakly sinuate. Dorsal margin of pronotal fovea directed caudad behind eyes ( Fig. 33 ). Nodal furrow nearly straight, removed by 1.6× its length from membranal suture, length 0.50, distance to membranal suture 0.80.

Fore tibia with thick, dense pad of short golden setae along anteroventral margin, covering anterior half of ventral face of tibia. Middle trochanter rounded. Middle femur with single moderately large, elongate, sharp subapical tooth, bordered basally by about 15 small black pegs, distally by about 3 similar pegs. Hind legs typical for genus, lacking unusual modifications. Lengths of leg segments as follows: fore femur–tibia–tarsal 1–tarsal 2 = 1.10/1.20/0.60/0.30; middle femur–tibia–tarsal 1–tarsal 2 = 2.30/2.00/0.70/0.40; hind femur–tibia–tarsal 1–tarsal 2 = 3.50/3.00/1.35/0.70.

Ventral abdomen with metaxyphus triangular, slightly concave, tip acuminate.

Male genitalia when viewed laterally ( Fig. 38 ) with ventral margin of proctiger broadly rounded, apex acute; posterior lobe of pygophore with posteroventral angle slightly obtuse, sharp, bearing a small setal tuft, posterior lobe of pygophore erect, apex truncate, posteriorly setiferous, not notched anteriorly on dorsal margin; paramere elongate, slightly tapering and curved anteriorly, posterior margin straight, apex rounded, reaching to dorsal margin of posterior lobe; lateral arm of basal plate broadly sinuate, of relatively even width throughout, apex rounded ( Fig. 38 ); aedeagus semicircular in lateral view, with numerous transverse folds.

Female: Length 9.50, width across pronotum 3.70 mm. Similar to male in general structure and coloration, but slightly larger and more robust in form ( Fig. 34 ).

Etymology. The name “tagula” is a noun in apposition, and refers to the type locality of Tagula Island, in the Louisiade Archipelago.

Discussion. Enithares tagula is similar in general size and coloration to E. atra from the Papuan Peninsula and E. insularis from the D’Entrecasteaux Islands, but may be differentiated by aspects of the male genitalia. The posteroventral angle of the pygophore is far more sharply defined in E. tagula than in either of the other two species (compare Figs. 17, 18 , 38 ), and the dorsal margin of the ventral lobe of the proctiger is more transversely truncate (compare Figs. 17, 18 , 38 ). The most pronounced difference lies in the structure of the LABP, which in E. tagula is gently sinuate in form when viewed laterally and of relatively even width throughout ( Fig. 38 ), rather than being broadly L-shaped and with a tapering distal arm that widens slightly at the apex, as seen in E. atra and E. insularis ( Figs. 17, 18 ). In addition to these genitalic characters, E. tagula has a broad vertex whose anterior width is greater than the length of the head when viewed dorsally, whereas in the other two species the vertex width is less than the head length.

Both E. tagula and E. insularis possess well-developed pads of thick, dense setae along the anterior margins of their fore tibiae, although these setae are darker and more promiment in E. insularis .

Ecological notes. At the Kalitau Creek type locality (CL 7190), E. tagula was taken in side pools amid bedrock along the main stream channel, and from pools along a rocky tributary. At a small, spring-fed stream nearby (CL 7192), this species was collected from scattered standing pools amid boulders in a bedrock channel.

Enithares insularis is apparently endemic to Tagula Island in the Louisiade Archipelago ( Fig. 55 ), although it is plausible that it might also occur on the other adjacent high islands in the Louisiades such as Panatinane and Rossel. Based on current records, E. tagula occupies the Tagula Island area of freshwater endemism (Area 38) as defined by D. Polhemus & Allen (2007).

Figures

FIGURE 55. Distribution of species in the E. atra group on New Guinea. Square = E. digitata Lansbury; circles = E. elongata Lansbury; triangles = E. insularis n. sp.; pentagon = E. tagula n. sp.

FIGURES 31–34. Enithares species in the E. atra group, dorsal habitus photographs. 31–32. Enithares peninsularis n. sp., male and female; specimens from Papua New Guinea, Central Prov., CL 7248. 33–34. Enithares tagula n. sp., male and female; specimens from Papua New Guinea, Milne Bay Prov., CL 7190.

FIGURES 35–40. Enithares species in the E. atra and E. bakeri groups, male genitalic complex, left lateral view. 35. Enithares elongata Lansbury; specimen from Papua New Guinea, Morobe Prov., Wareo. 36. Enithares ziwa n. sp.; specimen from Indonesia, Papua Prov., Ziwa River, CL 7100. 37. Enithares stylata Lansbury; specimen from Papua New Guinea, Morobe Prov., Wau, CL 1817. 38. Enithares tagula n. sp.; specimen from Papua New Guinea, Milne Bay Prov. Tagula Is., CL 7190. 39. Enithares bakeri Brooks, specimen from Indonesia, West Papua Prov., Aimasi River, CL 2651. 40. Enithares loria Brooks; specimen from Indonesia, Papua Prov., Siewa, CL 7085.

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.