Nikoulabasis pauta, Marinov & Rashni, 2025

Marinov, Milen & Rashni, Bindiya, 2025, A contribution to the Odonata fauna of Moala Island, Fiji. Part I: erection of three new species in genera Nesobasis Selys, 1891 and Nikoulabasis Ferguson et al., 2023 (Odonata: Coenagrionidae), Zootaxa 5637 (2), pp. 292-310 : 302-306

Nikoulabasis pauta sp. nov.

( Figs 10–12 )

Holotype. ♀ ( NZAC04231104 ), section of Wailevu creek about 500 m above Maloku village up to the Savukaratu waterfall , 18.5876S, 179.8741E to 18.5903S, 179.8744E, 151–260 m a.s.l., 4 May 2024, MM leg.

Paratypes. 1♀ ( USP_14009 ), headwaters of Waitabu stream, native forested lowland by Maloku village , 18.5945S, 179.8653E, 394 m a.s.l., 26 October 2020, BR leg .; 1♀ ( USP_14010 ), M1-Moala, Waitabu stream headwater , BR leg .; 2♀♀ ( NZAC04231105-6 ), same data as the holotype .

Additional material (tenerals): 3♀♀, section of Wailevu creek about 500 m above Maloku village up to the Savukaratu waterfall , 18.5876S, 179.8741E to 18.5903S, 179.8744E, 151–260 m a.s.l., 4 May 2024, MM leg .

Etymology. The species epithet originates from the Fijian word “ pauta ” [= powder] as a noun in apposition. It was selected for the intensive pruinosity of the body observed in majority of the specimens and is a key characteristic for distinguishing N. pauta individuals in the field.

Description of holotype

( Fig. 10 )

Head ( Fig. 10B–C ). Labium pale yellow; frontal part of head yellow on genae, bases of mandibles ascending dorsally to level of dorsal end of toruli, crossing frons as a bar below level of antennal bases, partly on the disk of labrum and anteclypeus; labrum yellow with blue hue, green between antennal bases and eyes; dark areas as follows: reddish tips of mandibles, approximately M-shaped black marking at the base of labrum, pale brown lateral on the bases of mandibles and anteclypeus, almost entire postclypeus, brown line at the junction between postclypeus and frons; rest of head predominantly black with dark yellow to orange spots on antero-lateral faces of toruli, dorsal end of scape, two spots at each of the inner borders of toruli, spot anteriorly at median ocellus; black continues at the rear part of the head save for yellow next to foramen, with intensive pruinescence on the ventral surfaces of the lobes; eyes discoloured.

Thorax ( Fig. 10A–B, E ). All dark with intensive pruinescence. Prothorax black with two lateral yellow spots on the anterior lobe. Pterothorax black on mesepisterum with slight metallic sheen, brown on the rest of the segments with yellow around, edges of alar ridges and ventrally on mes- and metinfraepisterna and weak streak at ventral edge of metepimeron; black spot on the metapleural suture. Legs predominantly dark with pruinescence mainly on the femora: coxae yellow anteriorly and brown posteriorly, trochanters yellow; femora dark brown with paler line along the posterior edges on outer faces; tibiae brown at the bases (darker on the inner surfaces) transforming to dark yellow at the junction with tarsi; tarsi dark yellow at the bases of the segments and dark at the tips; darker coloration deeper on the claws.

Wings ( Fig. 10D ). Venation black; pterostigma brown; FW: 18 Px, RP 2 at 7–7.5 th Px; HW: 16 Px, RP 2 at 6.5 th Px; arculus at 2 nd Ax in all wings.

Abdomen ( Fig. 10A ). Black on the dorsum running from the base to the 2/3 rd of S9, rest of the dorsum (last 1/3 rd of S9 and S10) blue; ventral parts of terga yellow dark to orange on S1–7, pale yellow lines along the ventral edges starting from S4; sterna black. Ovipositor yellow with black serration. Cerci ( Fig. 10F ) black aligned with the tip of the valves, styli dark with orange tips.

Measurements: AL 28, HW 23, HF 3.5, S 0.2, P 0.5, MDBE 1.82.

Variations of paratypes

Figure 11 presents variations observed in the intensity of the body pruinosity, and metallic sheen on the mesepisternum and posterior abdominal segments. Reduced pruinosity is a postmortem effect due to the prolonged exposure into the liquid medium used for storing the specimens. All live individuals possessed very densely pruinose thoraxes (except for the mesepisterna only) and rear part of the head (cf. Fig. 12 ). The blue on the posterior abdominal segments is expanded in three specimens and developed at the posterior edges of S8, the blue area on S 9 in one specimen runs on the middle section of the entire dorsum. The metallic sheen on the body is mostly dark green or violet when observed at various angles. Spots at the inner corners of toruli are obscured to missing in one specimen. Variations in wings—FW: 18–19 Px, RP 2 at 7.5–8 th Px; HW: 16 Px; RP 2 at 6–7 th Px.

Measurements: AL 27–28, HW 21.5–22.

Note. This taxon is erected based on females only. Three teneral Nikoulabasis males ( NZAC 04230646, NZAC 04230591, section of Wailevu creek about 500 m above Maloku village up to the Savukaratu waterfall, 18.5876S, 179.8741E to 18.5903S, 179.8744E, 151–260 m a.s.l., 4 May 2024, MM leg.; NZAC 04231108, Wailevu creek above the Savukaratu waterfall, 18.5910S, 179.8733E, 321 m a.s.l., 6 May 2024, MM leg.) were sampled soon after they emerged. One ( NZAC 04231108) was photographed in the field ( Fig. 13 ), kept alive for over 24 hours and then preserved in acetone. This specimen was the most likely candidate for the allotype; however, the age of the specimen made it very difficult to decide on the affiliation with the females assigned in here to N. pauta . Additionally, the structure of the posterior abdominal segments deviates from the idiognosis for the genus provided in Donnelly & Marinov (2024: 184). The paraprocts are 1/3 rd the length of the cerci (see Fig. 13 ) which is atypical for members of Nikoulabasis where all males known so far have them subequal to slightly longer.All specimens are available for future studies when more Nikoulabasis males from Moala Island are collected.

Differential diagnosis

The overall dark colour (almost unicoloured body save for blue areas on the dorsum of S9–10) and the dense pruinescence in females of N. pauta are unique and separate it from the other congeners. In the general body stature females N. pauta resemble members of N. crassa Donnelly & Marinov, 2024 . The similarity is increased by the presence of the pruinosity on the thorax as well as other body parts; the shape of the mesostigmal plate (dorsoposterior tubercle missing); and the origin of RP 2 (about midway between nodus and pterostigma). The posterior lobe of prothorax in lateral view is raised in a similar up-right position in members of the two taxa, however the posterior edge in N. crassa appears more invaginated, giving it a bilobed general outline in dorsal view (see fig. 203E in Donnelly & Marinov 2024: 206). The length of the ovipositor (valvae not surpassing the tip of cerci) separates N. pauta from N. crassa (valvae surpassing the tip of cerci). In this feature females of N. pauta are closer to the females of N. furcifer Donnelly & Marinov, 2024 . The blue dorsal spots on S9–10 are very similar in both taxa. Nikoulabasis furcifer females develop pruinescence as well, with the populations from Koro as the most notable example (see fig. 213 in Donnelly & Marinov 2024: 215–216). Females N. pauta are much darker, with yellow areas much reduced (cross bar on the frons, ventral edges of tergites and ovipositor valvae) whereas females of N. furcifer are more vivid yellow. The general paler appearance of N. furcifer is enhanced by the presence of a red areas developed ventrally especially on S4–6, missing in N. pauta .

Figures

FIGURE 10. Nikoulabasis pauta, holotype: A) habitus; B) head and thorax, dorsal and lateral view; C) head, frontal view; D) HW; E) posterior end of prothorax and mesostigmal plate; F) ovipositor.

FIGURE 11. Nikoulabasis pauta, variations of the colour patterns within the paratypes, thorax and posterior end of abdomen of four specimens.

FIGURE 12. Nikoulabasis pauta, colouration in life.

FIGURE 13. Nikoulabasis sp., teneral male.