Rhagovelia riu, 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 : 185-189

Rhagovelia riu new species

( Figs. 303–309 )

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: 1 winged male, 1 winged female, 90 wingless males, 101 wingless females, same data as holotype, CL 7190, D. A. & J. T. Polhemus ( USNM) ; 2 winged females, 15 wingless males, 22 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., along margins of main channel, CL 7194a, D. A. & J. T. Polhemus ( USNM, BPBM) ; 1 winged male, 1 winged female, 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 = 2.40–2.50 mm (x = 2.47, n = 5); width = 0.95–1.00 mm (x = 0.99, n = 5). Wingless female, length = 2.90–3.20 mm (x = 3.26, n = 5); width = 1.20–1.40 mm, (x = 1.29, n = 5). Winged male, length = 3.75 mm (n = 1); width = 1.45 mm (n = x). Winged female, length = 3.75 mm (n = 1); width = 1.45 mm, (n = 1).

Color: Dorsal ground colour black, marked with dark orange-brown on anterior pronotum, basal sections of antennae and legs orange-yellow ( Fig. 303 ). Head black, tylus, genae and rostrum brown, tip of rostrum piceous; eyes dark reddish black. Pronotum black, with transversely ovate orange-brown spot anteromedially behind head vertex, this orange-brown coloration not extending laterally onto pleurae. Mesonotum with numerous shining black microfoveae; metanotum, abdominal tergites and connexiva uniformly dull black, lacking shining areas. Antennal segment I with basal one-third yellow, distal two-thirds plus all of segments II–IV black. Legs generally shining black, with acetabula, coxae, trochanters, basal one-third of fore femur orange-yellow. Venter uniformly black.

Structural characters: Head moderately short, declivant anteriorly, with weakly impressed median line; length 0.35, width 0.67; length of eye along inner margin 0.25, anterior/posterior interocular space, 0.20/0.42. Pronotum short, width 0.87, length along midline 0.15, less than dorsal length of head, leaving mesonotum broadly exposed. Mesonotum smooth, bearing numerous microfoveae, humeri depressed, length along midline 0.65. Metanotum barely exposed, length along midline 0.05. Lengths of abdominal tergites I–VIII, respectively: 0.12: 0.12: 0.12: 0.12: 0.12: 0.13: 0.25: 0.10. 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 propleurae; 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 and posterior margins of all femora, and anterior margins of fore and hind tibiae; all trochanters lacking pegs or teeth; fore femur gently bowed, fore tibiae strongly bowed in lateral view, not flattened or expanded distally; middle femur and tibia with margins straight, not flattened or otherwise modified; hind femur weakly incrassate, lacking spines or teeth; hind tibia straight, slender, lacking spines or teeth ( Fig. 305 ).

Venter of head and thorax lacking small black denticles; meso- and metasternum bearing long, fine dark setae; all abdominal ventrites lying in same plane, lacking medial carinae.

Paramere small, moderately stout, ventral margin broadly rounded and bearing a few short, stout setae posteriorly, dorsal margin straight basally, with pre-apical notch, apex thumb-like, rounded ( Fig. 306 ). Proctiger small, compact, lacking basolateral or distolateral lobes; distal cone broadly rounded ( Fig. 307 ).

Lengths of antennal segments I–IV: 0.70: 0.48: 0.50: 0.45.

Lengths of leg segments as follows: femur, tibia, tarsal 1, tarsal 2 of fore leg, 0.90: 0.90: 0.01: 0.01: 0.13; of middle leg, 1.50: 1.35: 0.05: 0.70: 0.67; of hind leg, 1.12: 1.65: 0.02: 0.03: 0.25.

Wingless female: Similar to wingless male in general structure and coloration, with following exceptions: mesonotum broadly domed, shape roughly inverted trapezoidal, shorter posterior margin weakly anteriorly concave; mesopleural regions strongly depressed,concave when viewed from above; metanotum and adjacent medial abdominal tergite I upwardly tumescent, set with numerous long, erect black setae; lateral sections of connexival segments I–V folded inward over lateral portions of corresponding abdominal tergites, leaving abdominal laterotergites in a horizontal position facing upward; connexival margins strongly convergent posteriorly, meeting over posterior margin of abdominal tergite V and entirely covering tergites VI and VII ( Fig. 304 ), posterolateral connexival angles broadly rounded when viewed laterally, slightly domed upward in area of closest appression above tergites VI and VII; abdominal tergite VIII and proctiger lying in nearly vertical orientation, tergite VIII dull black, proctiger darker shining black; abdominal ventrite VII shining dark brown.

Winged male: Similar to wingless male in general structure and coloration, with following exceptions: pronotum greatly enlarged, width 1.45, length 1.50, completely covering meso- and metanotum, anterior margin bearing small, transversely ovate, dark orange patch anteromedially behind head vertex, bounded laterally by pale silvery pruinose areas; humeri enlarged, slightly protrusive laterally; posterior pronotal lobe broadly domed, lacking obvious foveae, posterior margin broadly angular, bearing numerous long, gently curving, semi-erect black setae; forewings uniformly dark blackish-brown, extending past apex of abdomen when intact, bearing 3 closed cells all in basal half of wing, consisting of two elongate cells basally followed by a single much smaller distal cell near the middle of the wing, set centrally between the posterior apices of the two basal cells.

Winged female: Similar to winged male in general body form and coloration, with following exceptions: body size larger, pronotum width 1.45, length 1.50, with humeri prominent.

Etymology. The name “riu ” is a noun in apposition, and refers to Mt. Riu, the highest mountain on the island of Tagula and source of Kolukolu Creek, along which the type series of this species was collected.

Distribution. Louisiade Archipelago; endemic to Tagula Island ( Fig. 309 ). The species range as presently known occupies the Tagula Island area of freshwater endemism (Area 38) as delineated by D. Polhemus & Allen (2007).

Discussion. Rhagovelia riu is a dark-colored member of the R. caesius group occurring on Tagula Island in the Louisiade Archipelago, and is superficially similar to Rhagovelia woa from Rossel Island, with which it shares the character state of having the second tarsal segment of the middle leg longer than the third. It may be separated from that species by the uniformly yellow coloration of all the coxae and trochanters (Figs, 303, 304), versus having the middle coxae and trochanters dark brown to black in R. woa ; the form of the female abdomen, which has tergite I produced upward to form a setiferous tumescence, versus being flat and angled downward in R. woa ; and by the structure of the connexival margins, which are strongly infolded over the lateral abdomen along their entire lengths ( Fig. 304 ), versus only on their posterior halves in R. woa .

Ecological notes. For descriptions of the habitats in which this species was taken, see the preceding discussion under R. tagula . At Kolukolu Creek, R. riu was taken on slow-flowing pools or at the heads of riffles ( Fig. 308 ).

Figures

FIGS. 303–307. Rhagovelia riu n. sp., structural details; specimens from the Tagula Island. 303. Wingless male, dorsal habitus. 304. Wingless female, dorsal habitus; 303 and 304 from Kolukolu Creek, CL 7194. 305. Male right hind leg, dorsal view; 306. Male left paramere, outer lateral view. 307. Male proctiger, dorsal view; 276–279 from Kalitau Creek, CL 7190.

FIG. 308. Kolukolu Creek, Tagula Is., Milne Bay Province, Papua New Guinea, CL 7194, type-locality for R. riu n. sp.

FIG. 309. Distributions of species in the R. woa subgroup in the Louisiade Islands.