Rhagovelia tagula, Polhemus, 2024

Polhemus, Dan A., 2024, Thirty-four new species of Rhagovelia (Heteroptera: Veliidae) from the East Papua Composite Terrane, far eastern New Guinea, Zootaxa 5400 (1), pp. 1-214 : 135-139

Rhagovelia tagula new species

( Figs. 227–233 , 240 )

Type material examined. Holotype, wingless male: PAPUA NEW GUINEA, Milne Bay Prov., Louisiade Archipelago, Tagula [Sudest] Island, Kalitau Creek , 1 km. upstream from head of estuary, 0–30 m., 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. & J. T. Polhemus ( BPBM) . Paratypes: PAPUA NEW GUINEA, Milne Bay Prov., Louisiade Archipelago, Tagula [Sudest] Island: 4 winged males, 2 winged females, 21 wingless males, 10 wingless females, same data as holotype, CL 7190, D. A. & J. T. Polhemus ( USNM, BPBM) ; 25 wingless males, 9 wingless females, small spring fed stream near Kalitau Creek , 45 m., 11°21'30"S, 153°14'40"E, water temp. 26 °C., 29 August 2002, 10:00–12:00 hrs., CL 7192, D. A. & J. T. Polhemus ( USNM, BPBM) ; 2 winged males, 2 winged females, 23 wingless males, 14 wingless females, Kolukolu Creek, near Araeda village , 0– 105 m., 11°26'45"S, 153°25'57"E, water temp. 23 °C., 30 August 2002, 11:00–16:00 hrs., CL 7194a, along margins of main channel, D. A. & J. T. Polhemus ( USNM, BPBM) ; 11 winged males, 13 winged females, 49 wingless males, 39 wingless females, Tagula Island , same data as preceding except CL 7194b, highest pool and small rocky tributary creek, D. A. & J. T. Polhemus ( USNM, BPBM) .

Description

Wingless male: Size: Length = 3.10–3.30 mm (x = 3.21, n = 8); width = 1.05–1.20 mm (x = 1.10, n = 8). Wingless female, length = 3.30–3.45 mm (x = 3.39, n = 4); width = 1.10–1.40 mm (x = 1.25, n = 4). Winged male, length = 3.15–3.50 mm (x = 3.35, n = 3); width = 1.35–1.40 mm (x = 1.38, n = 3). Winged female, length = 3.65–3.70 mm (x = 3.67, n = 2); width = 1.40–1.45 mm (x = 1.42, n = 2).

Color: Dorsal ground color black, marked with dark orange-brown on anterior pronotum and connexiva, basal sections of antennae and legs pale yellow to orange-yellow ( Fig. 227 ). Head black, tylus, genae and rostrum medium brown, tip of rostrum piceous; eyes dark reddish-black. Pronotum black, with transversely ovate dark brown spot anteromedially behind head vertex, this brown coloration not extending laterally onto pleurae. Mesonotum, metanotum and abdominal tergites dull black, lacking shining areas; connexiva black on inner halves, dark orange-brown on outer halves. Antennal segment I with basal half pale yellow, distal half plus all of segments II–IV black. Legs generally shining black, with acetabula, coxae, trochanters, basal half of fore femur, basal one-fourth of hind femur pale yellow. Venter black, genital segments orange-brown.

Structural characters: head moderately short, declivant anteriorly, with weakly impressed median line; length 0.35, width 0.80; length of eye along inner margin 0.36, anterior/posterior interocular space, 0.20/0.45. Pronotum relatively long, width 1.00, length along midline 0.80, leaving only extreme posterior margin of mesonotum exposed. Mesonotum length at midline 0.05. Metanotum length at midline 0.12. Lengths of abdominal tergites I–VIII, respectively: 0.20: 0.20: 0.16: 0.16: 0.16: 0.15: 0.40: 0.30. Connexiva with margins of even width throughout, straight, convergent posteriorly, posterolateral angles not modified, apices separated by entire width of tergite VIII.

Entire dorsum and laterotergites covered with fine appressed golden pubescence, intermixed with a few longer, erect black setae on head and central sections of abdominal tergites; legs and antennae thickly clothed with short appressed gold setae, with scattered long, erect black spines on anterodorsal faces of antennal segments I and II, anterior margins of all femora and tibiae, and posterior margin of middle tibia; long pilose brown setae present along posterior margins of all femora; fore and middle trochanters lacking pegs or teeth; fore femur gently bowed, fore tibia slightly flattened and expanded distally, with small concavity on ventral face adjacent to grasping comb; middle femur and tibia with margins straight, not flattened or otherwise modified; hind trochanter with 2–5 small dark pegs ventrally; hind femur highly incrassate, bearing two parallel rows of teeth, ventral row lying in area covered by infolded hind tibia and consisting of approximately 16 tiny black pegs basally, followed by 8–10 moderate sized black teeth, the most basal of these teeth being the largest, the remainder somewhat smaller but generally subequal in size, dorsal row consisting of about 8 black teeth, with the 3 middle teeth of larger size; hind tibia broadly and gently bowed, inner surface bearing a row of 18–20 small dark teeth, several teeth near the middle of this row of slightly larger size ( Figs. 229, 230 ).

Venter of head and thorax bearing numerous small black denticles on jugum and adjacent prosternum, and on fore, meso- and metacetabulae; meso- and metasternum plus all abdominal sternites II–VI bearing long, fine gold setae centrally; abdominal sternite II with moderately developed longitudinal carina medially, this carina continuing in less pronounced form onto sternite III; lateral sections of sternite VII to either side of midline broadly depressed; sternite VIII with longitudinal median carina.

Paramere small, stout, bean-shaped, distal half bearing scattered short, stout setae, apex broadly rounded ( Fig. 231 ). Proctiger with basolateral lobes well developed, angular; distolateral lobes moderately developed, rounded; distal cone narrow, tapering to a narrowly rounded apex ( Fig. 232 ).

Lengths of antennal segments I–IV: 0.75: 0.50: 0.60: 0.55.

Lengths of leg segments as follows: femur, tibia, tarsal 1, tarsal 2 of fore leg, 1.00: 1:05: 0.02: 0.01: 0.25; of middle leg, 1.50: 1.25: 0.06: 0.50: 0.70; of hind leg, 1.50: 1.35: 0.02: 0.06: 0.30.

Wingless female: Similar to wingless male in general structure and coloration, with following exceptions: posteromedial section of pronotum depressed, posterolateral sections of pronotum to either side of this depression bearing bushy tufts of erect, curling black setae; abdomen angled strongly downward and then upward, V-shaped when viewed laterally, the point of inflection occurring at posterior margin of tergite V (fourth visible tergite from above), connexiva weakly convergent and subparallel adjacent to abdominal tergites II–V, then angled sharply inward at 90° to midline of body adjacent to suture between abdominal tergites V and VI, then subparallel again but in closer proximity adjacent to abdominal tergites VI–VIII ( Fig. 228 ); posterolateral angles of first connexival segments bearing thick, inwardly-directed tufts of stiff black setae, similar stiff black setae originating on inner faces of sixth connexival segments and projecting vertically between closely parallel connexival margins; posterolateral angles of sixth connexival segments produced into long, finger-like posterior projections, apices of these projections bearing acuminate tufts of stiff black setae; proctiger lying in nearly horizontal plane due to upward angling orientation of posterior abdomen. Legs with middle femur broadly flattened centrally on ventral face; hind femur slightly incrassate, bearing a row of 5 small black teeth distally on posterior margin, consisting of a moderate-sized, sharp tooth basally followed by 4 much smaller teeth of progressively decreasing size; hind tibia lacking teeth. Ventral surface with only a few small black denticles on the acetabula; abdominal ventrites lacking carinae.

Winged male: Similar to wingless male in general structure and coloration, with following exceptions: pronotum greatly enlarged, width 1.40, length 1.30, completely covering meso- and metanotum, anterior lobe orange-brown, posterior lobe dark blackish-brown; humeri enlarged, slightly protrusive laterally; posterior pronotal lobe broadly domed, lacking obvious foveae, posterior margin broadly angular, bearing scattered long, gently curving, semi-erect black setae; forewings uniformly dark blackish-brown, with veins slightly darker, extending past apex of abdomen when intact, bearing 4 closed cells, consisting of two elongate cells in basal half of wing followed by two smaller cells distally near center of wing, the outer distal cell smaller than the inner cell. Hind femur less incrassate than in male, with armature somewhat reduced.

Winged female: Similar to wingless female in general structure and coloration, with following exceptions: pronotum greatly enlarged, completely covering meso- and metanotum, humeri enlarged, posterior apex angular, anterior lobe with transverse dark orange spot in area behind vertex, remainder of pronotum black, posterior angular section set with numerous tiny foveae, entire pronotum covered with short recumbent gold setae, these setae becoming longer and denser on posterior angular section; abdomen not reflexed, lying in a uniformly horizontal plane when viewed laterally; forewings uniformly dark blackish-brown, bearing 4 closed cells, consisting of two long cells in the basal half of the wing plus two smaller distal cells near the center of the wing, the outer distal cell smaller than the inner cell.

Etymology. The name “tagula ” is a noun in apposition, and refers to the island of Tagula, the largest in the Louisiades, to which this species is endemic.

Distribution. Louisiade Archipelago; endemic to Tagula Island ( Fig. 240 ). The species range as presently known occupies the Tagula Island area of freshwater endemism (Area 38) as delineated by D. Polhemus & Allen (2007).

Discussion. Within the R. papuensis group as a whole, R. tagula may be easily recognized by the transverse fold across the central portion of the female abdominal connexiva ( Fig. 228 ), with the posterior half of the abdomen behind this fold angled sharply upward at a 45° angle. The connixival margins immediately anterior to the transverse fold on each side bear thick, triangular tufts of stiff black setae, with similar setal tufts also present at the posterior connexival angles, and at the posterolateral angles of abdominal tergite VIII. By contrast, the male body form is similar to other members of the R. papuensis group, and the male genitalia are also similar to other members of this group, with a bean-shaped paramere ( Fig. 231 ), and a proctiger with well-developed, somewhat angular basolateral lobes, and more weakly developed, rounded distolateral lobes ( Fig. 232 ).

Ecological notes. Rhagovelia tagula was common along the margins of shaded, rocky streams draining the hill slopes of Tagula Island. The insects appeared to prefer streamlets and flowing pools with some degree of current, and were not common on quiet stream pools.

At Kalitau Creek (CL 7190) this species was found on a small, clear stream in a very rugged bed of dipping metamorphic Calvados Schist. The bed profile consisted of small rocky rapids and a few low cascades, alternating with long, deep pools. Collections were made here for about 2 km upstream from the head of the estuary.

This species was also taken on a small, spring-fed stream near Kalitau Creek (CL 7192), consisting of standing pools connected by shallow riffles in a bedrock channel with scattered large boulders. Base flow in this stream appeared to diminish significantly during the dry season, to a very low remnant trickling flow connecting the pools.

At Kolukolu Creek (CL 7194), R. tagula was taken from a swift stream flowing through boulder-strewn reaches, chutes and pools in metamorphic bedrock ( Fig. 233 ), which dropped over a waterfall approximately 20 high into a large, deep pool that marked the head of tide at the upper end of its mangrove-lined estuary.

Figures

FIGS. 227–232. Rhagovelia tagula n. sp., structural details; specimens from Tagula Is. 227. Wingless male, dorsal habitus. 228. Wingless female, dorsal habitus. 229. Male right hind leg, posterior view. 230. Male right hind leg, dorsal view; 227–230 from Kolukolu Creek, CL 7194. 231. Male left paramere, outer lateral view. 232. Male proctiger, dorsal view; 231 and 232 from Kalitau Creek, CL 7190.

FIG. 233. Kolukolu Creek, Tagula Is., Milne Bay Province, Papua New Guinea, CL 7194, habitat for R. tagula n. sp.

FIG. 240. Distributions of species in the R. yela subgroup in the Louisiade Islands, and R. suloga on Woodlark Island.