Nososticta tagula, Theischinger & Mitchell & Richards & Polhemus, 2023

Theischinger, Günther, Mitchell, Andrew, Richards, Stephen J. & Polhemus, Dan A., 2023, Systematics of the Nososticta salomonis complex (Odonata: Zygoptera: Platycnemididae), Zootaxa 5296 (2), pp. 101-146 : 128-129

Nososticta tagula sp. nov.

( Figs 50–54 , 56, 58 , Map 3 , Pl. 6)

Holotype. ♁, BPBMENT 0000081204, Papua New Guinea, Milne Bay Prov., Louisiade Archipelago, Tagula Is., Kalitau Creek , above estuary, 0–30 m a.s.l., 11°21’52”S, 153°14’26”E; 29-viii-2002, CL 7190, D.A. & J. T. Polhemus (CL 7190); deposited in the Bishop Museum, Honolulu, Hawaii.

Paratypes. 6 ♁♁, 1 ♀, BPBMENT 0000081205–81211, same data as holotype; deposited in the Bishop Museum, Honolulu , Hawaii .

Etymology. Tagula after the type locality Tagula Island in the Louisiade Archipelago; it is treated as a noun in apposition to the generic name.

Description of holotype (all available specimens (type series) apparently turned pale by the way of preservation (ethanol), meaning that in particular the larger now pale greyish blue areas would have been largely bright blue in life).

Head. Largely black; base of labium pale brownish yellow, anteclypeus greyish yellow marbled with grey, pleurostoma and transverse frontal bar from eye to eye very pale greyish blue, an ill-defined mark between antennal base and lateral ocellus pale brown as are apex of largely blackish brown scape and pedicel, antennal flagellum dark brown.

Thorax. Pronotum black, anterior lobe with two pale greyish yellow to bluish lateral spots on each side, the larger inner more yellowish spot detached and smaller outer more bluish spot only marginally separated from large mark of same colour on median lobe; propleura largely pale greyish blue, black along sutures and at rear of epimeron. Synthorax with pleura largely black except following pale greyish blue areas: ante-humeral patch, very slightly longer than 1/2 length of mesanepisternum, approximately twice as wide basally as dorsally, tip evenly rounded; patch covering about dorsal 4/5 length of mesepimeron, partly connected with stripe across whole length and anterior 3/4 to 4/5 of metepisternum; a subtriangular narrow-tailed patch across posterior half of metepimeron and posterolateral tip of meso- and metakatepisternum. Postcoxae blackish brown to black and pale greyish blue; poststernum pale brownish blue with ill-defined small, narrow patches of greyish brown. Legs: Coxae largely pale greyish blue, meso-and metacoxa anterobasally brown to black, trochanters black and pale greyish blue, legs otherwise black, with only very base of femora and part of basal 1/2 to 2/3 of metafemur pale greyish blue. Wings: membrane almost clear, venation black; pterostigma greyish brown, slightly more than twice as long as wide; postnodals 16/13–14.

Abdomen. S1 dorsally largely black, laterally pale greyish blue; S2 largely black, with distinct pale greyish blue apical dorsal mark, and pale greyish blue adjacent to genitalia; S3–7 dorsally black with blue basal mid-dorsal mark, the one on S7 very short, all ventrally margined greyish brown to dull yellow; S8 largely blue, narrowly lined black basally, more widely and irregularly lined black apically; S9 and S10 black. Superior anal appendages largely blue, inferiors brownish grey to brownish black.

Dimensions. Hind wing 18.8 mm; abdomen (including anal appendages) 31.3 mm.

Description of female

Head. Much as in male, but dark structures and areas darker, pale areas largely pale greyish yellow instead of pale greyish blue; no pale mark between antennal base and lateral ocellus detectable.

Thorax. Pronotum much as in male, but anterior lobe with ill-defined smaller outer mark only, vaguely connected to large mark of same colour on median lobe, posterior lobe with vertical dorsal and horizontal ventral lobe; propleura much as in male but pale areas largely pale greyish yellow instead of pale greyish blue. Synthorax with pleura largely black; pale greyish yellow areas restricted to: ante-humeral patch, very slightly longer than 1/2 length of mesanepisternum, very narrowly almond-shaped to almost parallel sided; mesepimeral patch reduced to tiny remnant completely fused with stripe across whole length and anterior 3/4 to 4/5 of metepisternum; subtriangular, narrow-tailed patch across posterior half of metepimeron; posterolateral tip of meso- and metakatepisternum. Postcoxae blackish brown to black and pale greyish yellow; poststernum pale greyish yellow with narrow elongate patches of dark greyish brown. Legs: Coxae largely pale greyish yellow, anterobasally brown to black, trochanters black and pale greyish yellow, legs otherwise black, with only very base of femora and part of basal 3/4 of metafemur pale greyish yellow. Wings: membrane rather clear, venation black; pterostigma black; postnodals 16/13–14.

Abdomen. S1 and S2 dorsally black, laterally largely pale greyish yellow; S3–7 dorsally black with greyish yellow dorsal mark very close to base, very tiny on S7, ventrally margined greyish brown to dull yellow; S8 black, ventrally margined greyish brown to dull yellow; S9 and S10 black. Anal appendages and inferior anal lamina pale yellow; supra-anal plate and valves brown to black.

Dimensions. Hind wing 19.5 mm; abdomen 29.3 mm.

Variation in the male paratypes. Small pale spots on anterior lobe of pronotum present or absent. Postnodals 15–16/12–14. Hind wing 18.1–19.4 mm; abdomen (including anal appendages) 30.3–31.5 mm.

Affinities. Based on the present study ( Fig. 6 ), N. tagula sp. nov. is closely allied with N. stueberi sp. nov. and N. boonei sp. nov., together these species comprise the sister group of N. chrismulleri .

Differential diagnosis. Among members of the N. salomonis complex, only N. africana and N. tagula sp. nov. have abdominal segment 2 dorsally marked with blue. Nososticta africana can be distinguished from N. tagula sp. nov. by having one or two blue antero-dorsal marks and one postero-dorsal mark on segment 2 (vs. only a blue postero-dorsal mark). Nososticta africana is known almost exclusively from the Bismarck Archipelago, while N. tagula sp. nov. is known only from the Louisiade Archipelago.

Distribution and habitats. Nososticta tagula is currently known only from Tagula Island in the Louisiade Archipelago ( Map 3 ). It has not been detected on other Milne Bay Islands despite extensive surveys across the region and may be range-restricted Tagula Island endemic.

Figures

MAP 3.—Distribution of Nososticta tagula sp. nov. in the Louisiade Archipelago.

FIGURE 6. Bayesian tree from concatenated (all genes) data set. Numbers above branches are BI posterior probabilities and ML bootstrap values shown only if ≥ 0.9 and 70%, respectively.

FIGURES 50–54. Nososticta tagula sp. nov. (50–52, 54) male: (50) synthorax, schematically; (51) abdominal segment 2, dorsal; (52) superior anal appendage; (53) female, synthorax, schematically; (54) specimen as photographed in ethanol.

FIGURES 55–65. Nososticta species. (55, 56) male abdominal segment 2, dorsal: (55) N. africana (Schmidt); (56) N. tagula sp. nov.; (57–65) synthorax, schematically: (57) N. africana (Schmidt), female; (58) N. tagula sp. nov., female; (59, 60) N. hedigeri sp. nov.: (59) male; (60) female; (61, 62) N. stueberi sp. nov.: (61) male; (62) female; (63) N. chrismulleri Theischinger & Richards, male; (64, 65) N. boonei sp. nov.: (64) female; (65) male.