Idiocnemis milou, Gassmann & Richards, 2019

Gassmann, Dirk & Richards, Stephen J., 2019, Two new damselflies of the genus Idiocnemis Selys from Gulf Province, Papua New Guinea (Odonata: Platycnemididae), Zootaxa 4560 (1), pp. 121-140 : 128-139

publication ID	https://doi.org/ 10.11646/zootaxa.4560.1.6
publication LSID	lsid:zoobank.org:pub:6581209C-8A69-4433-94D4-5E5FB7DA52D5
DOI	https://doi.org/10.5281/zenodo.5922854
persistent identifier	https://treatment.plazi.org/id/1E503A2B-FFE5-400B-A9DA-F12FAD0EFEEE
treatment provided by	Plazi
scientific name	Idiocnemis milou
status	sp. nov.

Treatment

Idiocnemis milou View in CoL sp. nov.

( Figs 2 View FIGURE 2 , 4 View FIGURE 4 , 6–8 View FIGURE 6 View FIGURE 7 View FIGURE 8 , 10 View FIGURE 10 , 13 View FIGURE 13 , 15, 18–19 View FIGURE 18 View FIGURE 19 , 22–23 View FIGURE 22 View FIGURE 23 , 26–28 View FIGURE 26 View FIGURE 27 View FIGURE 28 ) urn:lsid:zoobank.org:act:29502AED-F155-41A4-8348-65394A61C205

Holotype. ♂ Papua New Guinea, Gulf Province, Lakekamu Basin: small creek ca. 1.5 km SSW of Ivimka Camp (Camp coordinates: 146 ° 29.761'E, 7 ° 44.117'S, 120 m a.s.l.), 25-xi-96, S.J. Richards leg. ( SAMA 07-001524 About SAMA ). Deposited in the South Australian Museum. GoogleMaps

Paratypes. Papua New Guinea, Gulf Province, Lakekamu Basin. All specimens leg. S.J. Richards, collected from within ~ 2 km SSW of the following coordinates: 146 ° 29.761'E, 7 ° 44.117'S, at altitudes between 100–120 m a.s.l.: 1♂, 1 km transect, 24.xi.1996, field no 185 ( SAMA 07-001525 About SAMA ) GoogleMaps ; 1♂, Bulldog Track, 2 km south Ivimka Camp , 26.xi.1996, field no. 169 ( SAMA 07-001526 About SAMA ) ; 1♀, Bulldog Track, 1 km south of Ivimka Camp , 17.xi.1996, field no. 149 ( SAMA 07-001527 About SAMA ) ; 1♀, 1 km transect, south of Ivimka Camp, in forest, 22.xi.1996, field no. 153 ( RMNH); 1♀, Bulldog Track, adjacent Ivimka Camp , 23.xi.1996, field no. 154 ( SAMA 07-001528 About SAMA ) ; 1♂, small stream, 1 km transect, 26.xi.1996, field no. 158 ( SAMA 07-001529 About SAMA ) ; 1♀, 1 km transect, south of Ivimka Camp , in forest, 22.xi.1996 ( SAMA 07-001530 About SAMA ) ; 1♂, along 1 km transect, south of Ivimka Camp, 25.xi.1996, field no. 23 ( RMNH); 1♀, creek at end of ‘garden’ path, 300 m south of Ivimka Camp , 25.xi.1996, field no. 155 ( SAMA 07-001531 About SAMA ) . Papua New Guinea, Gulf Province, Dark End Lumber (DEL) area, all specimens collected within a 500 m radius of the following coordinates: 07°08.894S, 144°22.937E, ~ 55 m a.s.l.: 1♂, west of DEL Camp, 4.00 p.m., next to pool in forest, 06.x.1999, field no. 130 ( SAMA 07-001532 About SAMA ) GoogleMaps ; 1♂, field no. 85; 1♀, shady forest stream, adjacent DEL Camp, field no. 86 ( ZFMK ODO 2018 About ZFMK /2); 1♂, in forest at ‘unlogged’ site, nr. DEL Camp, 4.30 p.m., in shade over small stream, field no. 131( ZFMK ODO 2018 About ZFMK /3); 1♂, small “seepage” at DEL Camp, in sun, 3.00 pm, 04.x.1999, field no. 87 ( SAMA 07-001533 About SAMA ) ; 1♂, 1♀, DEL Camp, 03.x.1999, field no. 136 ( SAMA 07-001534 About SAMA – 35 About SAMA ) .

Etymology. It is a pleasure to name the new species after Mrs. Milout Martinot (Oegstgeest/ Netherlands), both in gratitude for her long-lasting personal friendship towards the first author, and in recognition of her engagement in civil initiatives for a more sustainable future. The name is placed as a noun by apposition.

Description of the holotype. Head. Labium, except for reddish-brown end-hook, yellowish-brown. Mandibles and maxillae of same colour, except distal parts of mandibles reddish-brown. Labrum orange-brown, darkened at upper margin and on medio-basal depression. Ante- and postclypeus medium brown with traces of black. Entire dorsal surface of head including antennal sockets purple, except for a central black marking on vertex shaped as in Fig. 4 View FIGURE 4 . Antennal scapus black with distal pale yellow ring, pedicellus medium brown, flagellum medium brown. Central black marking continuing on rear of head, turning ventrally into a diffuse colour pattern of light and medium brown.

Thorax. Prothorax with median lobe very slightly convex in lateral view; posterior pronotal lobe in dorsal view subtriangular but with lateral parts distinctly discontinued, lateral edges rectangular; posterior lobe not raised, in lateral view slightly bulgy except for posterior edge; prothorax dark brown to black, except for a diffuse pale yellow stripe reaching from lateral parts of anterior lobe across prothoracic pleura up to the mesostigmal laminae and areas more ventral to them. Synthorax ( Fig. 6 View FIGURE 6 ) dark brown to black with pale markings as follows: Mesepisternum with antehumeral purple stripes complete, evaginated halfway for nearly a third of entire course of stripe, this area black, which also covers dorsal carinal suture ( Figs 6 View FIGURE 6 , 27 View FIGURE 27 ). Metepisternum with a posterior squarish purple spot and a black area of same but slightly more irregular shape just anterior to it, the latter followed by a rather irregular purple rectangle covering roughly one fourth of metepisternum; all these pale markings connected ventrally (posteriorly) by a continuation of the pale marking that ends on mesepimeron in an irregular stripe. Anterior fourth of metepisternum deep black, bordered at its lower edge by a slightly diffuse but distinct pale yellow stripe. Metepimeron largely dark, except for a small diffuse pale yellow subtriangular spot at anterior upper corner; an even more diffuse pale yellow spot medially at lower margin. Underside of synthorax pale yellow anteriorly, pale orange posteriorly, with a pair of dark-brown stripes.

Wings. Entirely hyaline. Ac inserts at Ab. Arc at Ax2 (forewings), slightly distal to Ax2 (hindwings). Pt rhombic, costal side very slightly longer than anal side, reddish-brown. FW with 16 Px (left) to 17 Px (right), HW with 15 Px.

Abdomen. Largely medium brown to black, with pale markings as follows: S1 with a pair of roughly subtriangular purple spots. S2 with a pale pink dorsal marking shaped as an isosceles trapezoid widening distally, reaching from anterior end of segment to distinctly beyond halfway along segment. S3 to 6 with diffuse pale yellow-brown dorso-basal and subdistal markings ( Fig. 2 View FIGURE 2 ), the latter well defined against the dark brown rings that cover the posterior fifths of these segments; pale markings on S3 to 6 becoming less distinct posteriorly; S7 entirely dark, lacking bright dorsal markings; S8 with posterior half of dorsum and S9 with entire dorsum pink, with anterior dorsal edge of pink marking medially protruded at the level of dorsal carina; laterally, the marking reaches half way down the segments, edges roughly convex. Anal appendages in dorsal view strongly curved inwards; basal two-third of superior appendage comparatively straight in lateral view, apical part curved downwards. Superior appendage with large, basal protuberance shaped as an almost perfect right-angled triangle, slightly hooked apically; from the basal protuberance, a moderate inner shelf-like structure continuing distally bearing a subdistal spine-shaped process and in addition a smaller but distinct spine which is located between the subdistal process and the basal protuberance ( Fig. 10 View FIGURE 10 ). Inferior appendages robust and blunt apically, slightly curved upwards, about two-third the length of superiors. Appendages black, except for some diffuse orange-brown markings at inner sides and tips of superior ones, inner tubercle pale yellow.

Measurements of holotype (mm). FW 22.0, HW 20.5; abdomen including appendages 31.5.

Variation in males. The small spine between subbasal and subdistal process of superior appendage is lacking in some specimens ( Fig. 13 View FIGURE 13 ).

Measurements (mm). FW 21.5–22.0, HW 20.5–21.0 (n = 4); abdomen including appendages 30.5–32.0 (n = 2).

Female (paratypes). Head. Labium, maxilles and mandibles medium brown; the latter apically orange, with black tips. Labrum orange; ante- and postclypeus medium to dark brown; frons covered by a diffuse pale yellow stripe; its upper part, including antennal sockets, reddish-brown. Antennal scapus dark brown, the latter with pale yellow distal rings; pedicellus proximally and distally dark brown, medially light brown; flagellum dark brown. Posterior part of vertex, occiput and rear of head deep black, interrupted only by reddish-brown areas posterior to antennae as well as anterior and lateral to ocelli, by a pair of conspicuous pale yellow subtriangular postocellar spots (original coloration presumably faded) and a diffuse pale yellow stripe situated anteriorly and parallel to occipital ridge, isolated from postocular spots and protruding anteriorly between the posterior ocelli ( Fig. 15).

FIGURE 25. Idiocnemis lakekamuensis sp. nov., ♀, Lakekamu, terminal abdominal segments in latero-dorsal view.

Thorax. Prothorax with median lobe very slightly convex in lateral view; pronotum largely black-brown, pleura pale yellow. Anterior part of median lobe with a pair of slightly diffuse roundish to slightly oval black spots each covering a distinct depression of the median lobe ( Fig. 18 View FIGURE 18 ). Posterior pronotal lobe comparatively long, about same length as median lobe, not raised in lateral view, shaped as broadly rounded subtriangle with rather obtuse posterior edge and with lateral edges distinctly subrectangular; edge of posterior pronotal lobe broadly and clearly demarcated from its central part both in dorsal and lateral view, central part slightly bulgy ( Figs 22 View FIGURE 22 , 23 View FIGURE 23 ). Synthorax with coloration similar to male, but more diffuse and much paler. Anterior pale marking on metepisternum dorsally distinctly widened, the dark spot posterior to it narrowed dorsally. Underside of synthorax as in male.

Wings. FW with 16 (right) to 17 (left) Px, HW with 15 Px (n=5). Arc distinctly distal to Ax2. Pt as in male but shape more equilateral. Otherwise as in holotype.

Abdomen. Mainly black; similar to male, but with the following differences: S1 with a pair of subquadrangular whitish spots on dorsal half of segment; S2 with a dorsal elongate pale yellow marking which has its posterior corners extended into narrow stripes that extend halfway down the segment laterally. S3 to 7 with diffuse pale yellow markings, similar to male but less distinct. S8 to 10 each covered by a pale yellow marking dorsally, dorsal colour diffusely intermingled with black (S8), intruded by an anterior medial dark area (S9) or with an anterior half-circular black marking (S10); S 8 to 9 almost entirely covered by pale yellow in some specimens. Sternites of S8 dark brown to black, those of S9 yellow. Cerci yellow, their tips narrow, sharply pointed, darkened. Valvae with upper part yellow or with at least traces of yellow, lower part dark brown; visible part of ovipositor yellow. Styli medium to dark brown, apical parts yellowish.

Measurements (mm). FW 21.0–23.0, HW 20.0–22.5 (n = 6); abdomen including valvae 29.0 (n = 3).

Differential diagnosis. The new species, along with I. lakekamuensis sp. nov., belongs to the smallest species of the I. bidentata species group and may be easily distinguished from all congeners by its thoracic colour pattern. The black dorsal synthoracic marking extends medially into the antehumeral stripes ( Fig. 27 View FIGURE 27 ), taking a roughly cross-shaped overall shape in dorsal view without, however, fully subdividing the latter as is the case in I. nigriventris Lieftinck, 1937 and I. obliterata Lieftinck, 1932 . In lateral view, the colour pattern is characterized by the distinct bright mesepimeral marking showing two upper subrectangular offshoots, of which only the anterior one is in partial contact with the antehumeral stripe. This pattern most closely approaches that of I. lakekamuensis sp. nov. In that species, however, the anterior subrectangular element is fully in contact with the antehumeral stripe. The male superior appendage of I. milou sp. nov. is usually characterized by a small spine halfway between the subbasal and subdistal processes. A similar minute spine is present in I. schorri , but in that species the spine is situated close to the subbasal process (cf. Gassmann et al., 2016: figs 14a, b). In cases where the minute spine is lacking, the superior appendages of I. milou sp. nov. are reminiscent of those of I. mertoni ( Fig. 12 View FIGURE 12 ). However, both the subbasal and the subdistal process are more distinctly pointed in the new species.

Distribution and habitats. Currently known only from Gulf Province in southern central New Guinea, between the Kikori River lowlands in the west and the Lakekamu Basin in the east. Like I. lakekamuensis sp. nov., this species is closely associated with small, clear-flowing seepages and streams in lowland rainforest where it perches on low vegetation and twigs in patches of sunlight. A detailed description of the vegetation, climate, fauna and flora of the type locality can be found in Mack (1998).