Nesobasis brachycerca, Tillyard, 1924

Habitat association of N. brachycerca View in CoL

A total of 26 individuals of N. brachycerca were collected (22 from Rabi Island and four from Vanua Levu). Habitat characteristics were recorded for 13 of them ( Table 1 View TABLE 1 ). This study indicated that N. brachycerca prefers a highly shaded system with native riparian vegetation. It was frequently perched on the native deciduous tree Girroniera celtidifolia (locally known as Sisisi). Other native trees that the species preferred were Atuna racemosa and Barringtonia sp. including the native perennial shrub Melastoma sp.

The majority (62%) of the individuals were perched; all, but one (on rock) on native plants: 86% native deciduous trees and 14% native perennial shrub. The individuals recorded in flight were all on the TRB. Two individuals were recorded on the TLB and these were perched on the native plants ( Barringtonia sp. and Melastoma sp. ). Environmental conditions in situ results indicate that N. brachycerca were recorded during warm weather (average temp. =31.0 ± 0.49 oC, range: lowest= 30.3 ± 0.49 oC and highest= 31.9± 0.49 oC) in areas with dense canopy cover (average density = 97.6 ± 1.87%, range: lowest= 94.4 ± 1.87% and highest = 99.7 ± 1.87 %). The Light intensity ranges from 290 ± 389.22 Lux to 1517 ± 389.22 Lux with an average of 765.2 ± 389.22 Lux and the average relative humidity was 75.2 ± 2.60%.

Description of female

( Figs 3–9 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 )

Material: 1♀ (NZAC04225776, NZAC), FIJI, Rabi Is , upper reach of Tabiang creek (for coordinates see Material and Methods)

Other specimens collected: 1♀ (USPac_12593); 2♀♀ (NZAC04200826–7)—all from the same locality in Tabiang creek , Rabi Is .

Head ( Figs 3–5 View FIGURE 3 View FIGURE 4 View FIGURE 5 ). Labium pale yellow; mandibles yellow at the bases and darker reddish at the tips; labrum pale yellow along the anterior edge becoming darker towards to disk to almost completely black on the posterior half; anteclypeus pale yellow-green at the middle and pale brownish on both sides; postclypeus entirely black; pale yellow-green on: frons (interrupted by a narrow black stripe joining black on the dorsum with the base of the postclypeus) continuing upward along the eyes up to the level of tip of scapus, anterior faces of torullus, scapus and pedicellus, oblique lines behind antennal bases, small spot anteriorly to the medial ocellus; flagellum dark red to brown; rest of the dorsal surface of cranium black with green metallic sheen; rear part of head yellow with dark spots close to the foramen; eyes discoloured.

Thorax ( Figs 3 View FIGURE 3 , 5–6 View FIGURE 5 View FIGURE 6 ). Prothorax with postero-lateral margin of median lobe extruded into a keel; colouration black to the dorsum, dark yellow on the extrusions, pale blue on the rest. Pterothorax black as follows: disk of the mesostigmal plate, 2/3 of mesepisternum (dark yellow to orange along the dorsal carina), dark spot posteriorly sitting on the mesopleural suture close to the alar area, irregular shaped bar on the disk of mesepimeron, longitudinal bar on the dorsal part of mesinfraepisternum, faint streak on the interpleural suture almost touching alar area, spot sitting posteriorly on the metapleural suture, posterior end of posternum; dark yellow developed on remaining areas of mesepisterna, almost entire mesepimeron; rest of the pterothorax pale blue starting from dorso-posterior part of mesepimeron and becoming paler towards the ventral part of the thoracic capsule to pale yellow on metinfraepisternum and anterior 1/3 of metepimeron. Legs yellow with black spines; black areas developed on posterior surfaces on all femora, fain brownish streak along the posterior surface of the front tibiae; claws yellow at the base, darker reddish at the tips. Mesostigmal plate low without raised corners, concave on the disk; pits developed between the plate and dorsal carina.

Wings ( Figs 7–8 View FIGURE 7 View FIGURE 8 ) hyaline with generally dark venation (paler proximally) and yellow pterostigma; CuP about half way between the two antenodal veins sitting at the place where Cup&AA leaves the wing margin; arculus at or slightly distal of the second antenodal vein; IR 2 and RP 3+4 touching to almost confluent below subnodus originating slightly distally of it; RP2 at about seventh (FW) or sixth (HW) postnodal; MA almost straight for most of its length and zigzagged at the level of seventh (FW) or eight (HW) postnodal; MP curved at its origin from the discoidal cell and then straight for its length ending at the wing margin at about the ninth postnodal vein; one row of cells distally of pterostigmata (HW with the first cell crossed). Nodal Index 14-2 / 2-14 in FW, 13-2 / 2-13 in HW.

Abdomen. Entirely black on the dorsum; ventral part predominantly yellow saved for pale blue on S1, bases of S2, laterally on S10; all sterna yellow, all but S1 having a black line along the middle ridge of the segment not reaching the two ends of the segment; no spine on S8 anterior of the ovipositor ( Fig. 9a View FIGURE 9 ); the latter yellow, reaching in length the posterior end of paraproct, finely dentate, stylus dark red with dark yellow tip surpassing the posterior end of the paraproct; cercus dark brown to black, triangular shaped, slightly dorso-ventrally compressed; posterior edge of S10 flattened and compressed forming a roof-shaped structure ( Fig. 9b View FIGURE 9 ).

Measurements: AL 30.5; HW 21.0; HF 2.9; S 0.2; P 0.4; P/S 2; PR 6.7.

Variations in females

One mature and two teneral specimens were investigated. They all come from the same locality with the female described above. Figure 10 View FIGURE 10 compares all four females. The most notable difference in the mature specimens was observed in the width of the black bar on the metepisternum and colouration of the posterior faces of the legs especially femora (cf. Fig. 10a–b View FIGURE 10 ). Teneral specimens, however, differ significantly even in the general outlines of the thoracic markings (cf. 10c–d). The darker shades on the side of the pterothorax of the tenerals follow the outlines of the orange area in mature females especially on the mesothorax. On the metathorax of mature specimens this area is replaced by the blue colouration with slight traces of orange around the black spots on the metepisternum. Note that the teneral females also have the dark spots on meso- and metapleural sutures developed, but not the streak on the intersegmental suture. Dark markings on mesepimeron and mesinfraepisternum are not present on tenerals either.

Other significant age-dependant changes are in the colouration of: frontal part of the head (cf. Fig. 10e–g View FIGURE 10 ) and the posterior abdominal segments observed in dorsal view (cf. Fig. 10h–j View FIGURE 10 ).

Face of teneral specimens has traces of dark on labrum, postclypeus and frons (Fig. Fig. 10f–g View FIGURE 10 ) which mark black areas which will develop in mature specimens ( Fig. 10e View FIGURE 10 ).

Teneral specimens have two dark spots at the base of S9 and almost entire dorsum of S10 pale; cerci and styli are pale too ( Fig. 10i–j View FIGURE 10 ). In contrast the basal dark spots on S 9 in mature female almost connect to a near entire dark area (interrupted at the middle only) and join another dark surface developed at the posterior end of the segment; S10 is also dark at the base, as well as cerci and styli ( Fig. 10e View FIGURE 10 ).

Description of male

( Figs 11–18 View FIGURE 11 View FIGURE 12 View FIGURE 13 View FIGURE 14 View FIGURE 15 View FIGURE 16 View FIGURE 17 View FIGURE 18 )

Material: body morphology except wings 1♂ (NZAC04225777, NZAC), wings 1♂ (NZAC04225778, NZAC), both males from upper reach of Tabiang creek (for coordinates see Material and Methods).

Other specimens collected: 13♂♂ USPac_12580–92 (all from Tabiang creek ); 1♂ USPac_12594 (Vanua Levu, mid section of an unnamed creek above the Mika Tings Farm settlement, 16° 35’ 40.44” S, 179° 46’ 54.49” E, 6 December 2022); GoogleMaps 3♂♂ NZAC04200820–22 (Vanua Levu, lower section of an unnamed creek above the Mika Tings Farm settlement, 16° 35’ 34.13” S, 179° 47’ 13.84” E, 6 December 2022); GoogleMaps 3♂♂ NZAC04200823–25 (all from Tabiang creek) GoogleMaps .

Head ( Figs 11–14 View FIGURE 11 View FIGURE 12 View FIGURE 13 View FIGURE 14 ). Citron yellow developed as follows, bases of mandible (tips dark red), ¾ of labrum, anterior of anteclypeus, genae upward along the eyes to the level of tip of scapus, yellow becoming darker on the frons interrupted at the middle by a dark bar connecting the black on the dorsum with the postclypeus, anterior faces on torullus, scapus, pedicellus, dark yellow are two oblique bars behind the bases of antennae and a small spot anteriorly of the median ocellus; rest of the head black which descends on the rear of the head from the level of occipital lobes close the border line with eyes; eyes in life ( Fig. 13 View FIGURE 13 ) bicoloured dark red dorsally, green-yellow ventrally.

Thorax ( Figs 11 View FIGURE 11 , 14 View FIGURE 14 ). Predominantly dark red with black on the dorsum (running on pronotum and occupying 2/3 of mesepisternum saved for a faint dark red line on the middle of the dorsal carina) and yellow on the venter which ascends onto anterior areas of mes- and metepisternum, entire metinfraepisternum as well as separate spots and streaks sprinkled on the mesepisternum, laterally on the prothorax and posternum; other black areas developed as follows: disk of mesostigmal plate at the anterior half of it, two spots sitting posteriorly on the mes- and metapleural suture close to the alar areas, small streak at the posterior corner of interpleural suture, roughly triangular spot on mesinfraepisternum, oblique bars with diffused edges anteriorly on mespisternum nearly touching the posterior corners of the triangular areas on mesinfraepisternum, posterior end of posternum; faint small spot on the intersegmental suture anteriorly of the dark streak. Legs almost entirely citron yellow with black spines saved for reddish spots on the coxae, dark tips of the femora, posterior faces of the front tibiae along the outer half of them; claws yellow at the bases becoming darker towards the tips.

Wings ( Figs 15–16 View FIGURE 15 View FIGURE 16 ) mostly hyaline (HW with microsculpture at around the level of pterostigma, Fig. 16b View FIGURE 16 and slightly fumed along the row of the cells distally) with dark pterostigma; rest of wing venation as in the female. Nodal Index 14-2 / 2-14 in FW, 14-2 / 2-14 in HW.

Abdomen black dorsally (saved for a faint dark red line at the middle) to the basal 1/3 of S9, remaining of the segment as well as almost entire S10 red; red developed as follows: larger area laterally on S1, irregular spots laterally on S2, posterior 2/3 area bordering the black on S7 continuing on entire S8 with both last segments having separate red spots sprinkled on the yellow at their ventral parts; remaining areas of all terga yellow becoming paler ventrally; sterna yellow on S1, anterior lamina on S2, S3 becoming pale yellow on the remaining segments; middle ridge of sterna coloured with orange (S3–5) and dark lines (S6–8), almost all nearly touching each other forming an almost complete coloured line up to S7 where the colouration is interrupted at the posterior end, dark on S8 sternum wider than the rest not reaching both ends of the segment.

Penis as on Fig. 17 View FIGURE 17 .

Appendages ( Fig. 18 View FIGURE 18 ): cercus shorter than paraproct, latter about half length of the width of S10; cercus with the outer edge outgoing at an angle of 120 o, almost entire black dorsally saved for dark red areas starting about midway and continuing to the outer surface areas, yellow ventrally, basal tubercles touching at the point of divarication; paraprocts with pincers-like projections at the outer corners curved inwardly and concavity close to the point of contact between them, almost entirely dark orange with black tubercle-like structure laterally at the junction with S10 and at the tips of projections, palest parts are areas around the inner concavity.

Measurements: AL 37.5; HW 23.5; HF 3.5; S 0.2; P 0.5; P/S 2.5; PR 8.3.

Variations in males

Tillyard (1924) description of the holotype male is short, but concise and accurate for the general colour appearance of the specimens classified under N. brachycerca . We add more details here from the head (not described by Tillyard), some dark markings laterally on the thorax and abdomen, as well as provide the illustration of the penis for the first time. Terminal abdominal appendages illustrated in Tillyard (1924: fig. 18) need to be corrected especially for the dorsal view of the cerci which are shown as a single unit (cf. Fig. 19a View FIGURE 19 ). The morphology of the cerci of the holotype is shown on Figure 19b View FIGURE 19 and correction of Tillyard’s figure is proposed on Figure 19c View FIGURE 19 .

More variations are illustrated on Figure 20 View FIGURE 20 for the colouration of the labrum, side of pterothorax and sculpture around pterostigma. Labrum varies in the width of the posterior black cross bar which occupies the mainly the border of the labrum and antefrons ( Fig. 20a View FIGURE 20 ), nearly half area of the labrum ( Fig. 20b View FIGURE 20 ) to almost entire surface saved for the bright yellow anterior edge of it ( Fig. 20c View FIGURE 20 ). Variations of the pterothorax are in the intensity of the black markings on the border area between mesepimeron and metepisternum: no dark spots around the intersegmental ( Fig. 20d View FIGURE 20 ), another black streak appears anterior to the one described for the male above ( Fig. 20e View FIGURE 20 ), both present ( Fig. 20f View FIGURE 20 ), additional round dark spot on the suture anterior of the basal marking with different level of intensity ( Fig. 20g –k View FIGURE 20 ). Intensity of the darkening of the sculpture around the pterostigma is illustrated on Figure 20l–q View FIGURE 20 . Note that some specimens have double-celled area distally of the pterostigma ( Fig. 20m –n View FIGURE 20 ).

One last variation worth mentioning is the change of the colour of the dorsum of S9–10 which in some specimens loses its red intensity and is slightly brownish. This is not illustrated in here because is unclear if this change is related to age or is dependant of the method of preservation.