Idiocnemis lakekamuensis, 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 : 122-128

Idiocnemis lakekamuensis sp. nov.

( Figs 1 , 3 , 5 , 9 , 11 , 14 , 16–17 , 20–21 , 24 –25, 28) urn:lsid:zoobank.org:act:E6CCE2B9-ECA7-4445-B1CE-3D74038C3370

Holotype. ♂ Papua New Guinea, Gulf Province, Lakekamu Basin: 1 km south of Ivimka Camp (Camp coordinates: 146 ° 29.761'E, 7 ° 44.117'S, ~ 120 m a.s.l.), adjacent to seepage, 24.xi.1996 (field envelope no. 21(1)) ( SAMA 07-001510 ). Deposited in the South Australian Museum.

Paratypes. Papua New Guinea, Gulf Province, Lakekamu Basin. All specimens leg. S.J. Richards, collected from within ~ 1.5 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’, south of Ivimka Camp , in forest, 22.xi.1996, field envelope no. 153 ( ZFMK ODO 2018 / 1) ; 1♂, ridge trail, beside river, sitting on dry stick, 22.xi.1996, field no. 168 ( SAMA 07-001511 ; 1♂, Ivimka Camp , 29.xi.1996, field no. 142 ( SAMA 07-001512 ) ; 2♂♂, 1.5 km south of Ivimka Camp , 27.xi.1996, field no. 148 ( SAMA 07-001513 – 4 ) ; 1♂, 500 m south of Ivimka Camp , perched in shade, 18.xi.1996, field no. 188 ( RMNH) ; 1♀, approx. 500 m south of Ivimka Camp, on Bulldog Track , 20.xi.1996, field no. 145 ( SAMA 07- 001515 ) ; 1♀, Bulldog Track, 1 km south to Ivimka Camp , 17.xi.1996, field no. 149 ( SAMA 07-001516 ) ; 1♂, 1♀, site #4, garden, in flight near stream, 29.xi.1996, field no. 141 ( SAMA 07-001517 – 18 ) ; 1♂, trickle along 1 km transect nr. Ivimka Camp , 24.xi.1996, [apps. lacking], field no. 167 ( SAMA 07-001519 ) ; 1♂, Ivimka Camp , 24.xi.1996, field no. 21(2) ( SAMA 07-001520 ) ; 1♂, Ivimka Camp , 29.xi.1996, field no. 184 ( SAMA 07-001521 ) ; 1♂, 500 m southeast of Ivimka Camp , 16.xi.1996, field no. 156 ( SAMA 07-001522 ) ; 1♂, Ivimka Camp , 27.xi.1996, field no.147 ( SAMA 07-001523 ) .

Etymology. The species is named after the Lakekamu Basin in Papua New Guinea’s Gulf Province, the only location from where it has been recorded.

Description of the holotype. Head. Labium dirty yellow, with median incision roughly arc-shaped. Labrum yellow-orange. Genae dark brown laterally, dirty yellow ventrally. Anteclypeus medium to dark brown; postclypeus brown-black. Frons and vertex, including antennal sockets, purple. Vertical black marking small, confined to area between ocelli, medially only slightly divided, posteriorly diverging, continuing laterally on occipital ridge from where it connects to black coloration of rear of head ( Figs 1 , 3 ).

Thorax. Prothorax with median lobe only slightly convex in lateral view; posterior lobe roughly subrectangular in outline, posterior edge very slightly rounded; dorsum of prothorax black, diffusely limited against a yellow lateral area which extends onto mesostigmal plates; pleura with lower half black, except for a diffuse subtriangular intrusion originating from lateral bright marking which covers upper half of pleura. Synthorax ( Fig. 5 ) with antehumeral stripe covering almost entire mesepisternum, dorsal carina marked with black; antehumeral stripe yellow-brown, with remnants of purple (probably original coloration). Metepisternum with posterior three-fourths covered by a purple bar which either completely (left side), or nearly (right side), encircles a semi-oval black spot in its middle, the latter forming a narrow connection to posterior part of black mesepisternal marking (on left side); anterior fourth of metepisternum dark black, distinctly limited against purple marking. Metepimeron with anterior part black except for a bright yellow stripe traversing its lower half horizontally and, posterior to the latter, a medium brown stripe which is somewhat bulged out posteriorly. Legs yellow-orange, joints and adjacent areas darkened. Underside of synthorax pale yellow, with a pair of black stripes.

Wings. Hyaline. Arc inserting at or slightly distal (right HW) to Sn. R4 distal to Sn, less distinctly so in forewings. Pt rhombic, medium to dark brown. FW with 17 Px, HW with 15 Px.

Abdomen. Ground colour medium to dark brown, with bright markings as follows ( Fig. 1 ): S1 with a roughly half-circular dorsal purple marking, S2 with a sub-quadrangular but posteriorly widened purple marking, S3 with a yellow-orange basal dorsal spot and a subdistal ventral bright marking of same colour; S4 to 5 with bright markings similar to those in S3 but less distinct. S6 to 7 with no pale markings except for a very weak and diffuse yellow ventro-basal marking on S6. Slightly more than posterior dorsal half of S8 as well as entire dorsal surface of S9 with a greyish-brown (probably originally purple) marking, its corners rounded, anterior margin rather straight. Superior appendage with small subbasal process, apically rounded, and a subdistal almost finger-shaped subacute process which is longer than subbasal one ( Figs 9 , 11 ). Colour of appendages dark brown, inner tips pale yellow.

Measurements holotype (mm). FW 21.5, HW 20.0; abdomen including appendages 31.5.

Variation in males. Generally similar to the holotype. The metepisternal black spot within the purple bar can be either irregular or almost perfectly rectangular. In two specimens it is entirely enclosed by the bright mesepimeral marking on both sides of the synthorax.

Measurements (mm). FW 20.0–22.5, HW 18.5–21.0 (n = 13); abdomen including appendages 29.5–33.5 (n = 9).

Female (paratypes). Head. Labrum, genae and frons dirty-yellow, ante- and postclypeus intermingled with brown. Antennal segments dirty-yellow to orange-brown. Diffuse black vertical marking extends as a broad stripe between eyes, intermingled with some yellow around ocelli and antennae, continuing posteriorly in two black lines lateral to an orange stripe marking occipital ridge. In one specimen, black marking reduced to traces of black with largest portion of black centred around ocelli. Two pale turquoise subtriangular postocular spots present (original coloration probably faded) ( Fig. 14 ). Rear of head yellow.

Thorax. Prothorax with pronotum dark bluish-black, median pronotal lobe with a pair of diffuse black spots close to border with anterior lobe ( Fig. 16 ). Posterior pronotal lobe subrectangular, posterior edge only very slightly bulged out medially ( Figs 17 , 20 ). Synthorax with colour pattern similar to male, but far less distinct. Mesepisternum with a diffuse pale yellow marking adjacent to anterior third of humeral suture and a weak yellow marking well before the suture’s posterior end; mesepisternum otherwise diffuse brownish, lacking clearly recognizable antehumeral stripes. Mesepimeron with anterior part black as in male, but with diffuse yellow markings at the areas where the male has its grey-purple markings. Metepisternum and metepimeron as in male, but less distinct.

Wings. Pt asymmetric, anterior side distinctly longer than posterior side. Otherwise as in male. FW with 16–17 Px, HW with 13–14 Px.

Abdomen. Ground colour black, with light markings as follows. S1 with pair of diffuse pale turquoise spots covering posterior two-third of dorsal surface, separated from each other except for a thin connection along border of S1 and S2. S2 with a pair of elongate pale yellow dorsal spots each roughly shaped as an asymmetric triangle. S3–7 dorsally with a distinct basal pale yellow spot and a smaller subdistal spot of same colour, both losing intensity towards posterior segments. S8–9 with a pair of large diffuse but (except for the teneral specimen from Bulldog Track [field no. 149]) distinctly separate pale yellow spots. S10 with a confluent pair of diffuse pale yellow spots, covering roughly posterior half of dorsal surface of that segment, isolating a black triangular marking on its anterior dorsal half. Cerci pale yellow ( Figs 24 , 25). Upper lateral part of valvae and tergite of S 8 pale yellow.

Measurements (mm). FW 20.0–21.5, HW 19.0–20.0 (n=3); abdomen including valvae 27.5–29.5 (n=3).

Differential diagnosis. The male of this species is readily identified by the colour pattern on its head. The central black marking on the vertex, which is subquadrangular in most members of the species group, is distinctly reduced to form a rather diffuse black area filling the space between the three ocelli. In only two other species, I. dagnyae Lieftinck, 1958 , and I. mertoni Ris, 1913 , is the black marking occasionally reduced as well, but never to such an extent as in I. lakekamuensis sp. nov. The male of the present species is also clearly distinguished from congeners by the shape of the superior appendage ( Figs 9 , 11 ) which is characterized by a short and pointed subbasal process and a hook-like, slightly pointed subdistal process. This arrangement is distinctly different from that in most other species of the Idiocnemis bidentata group where the subbasal process is shaped as a prominent subtriangular protrusion. Only I. pruinescens has a similarly shaped superior appendage; however, in that species the subbasal process is longer than in the present species, and rather blunt (cf. Gassmann 2000). The female of I. lakekamuensis sp. nov. can be recognized by its posterior pronotal lobe which has a characteristic subrectangular shape not similarly found in any other member of the species-group. The female’s head colour pattern is similar to that in I. inaequidens Lieftinck, 1932 , I. schorri Gassmann, Richards & Polhemus, 2016 , and the new species described below, in having the vertex of the head nearly entirely covered in black. The extent of the black marking, however, is less than in I. inaequidens and I. schorri , with the areas around the antennae left free of black, but the black coloration is more extensive than in the new species described below.

Distribution and habitats. Southern Papua New Guinea ( Fig. 28 ). Known only from the Lakekamu Basin in Gulf Province where I. lakekamuensis sp. nov. was found perched in sunlight on low vegetation along small, clearflowing seepages and streams in lowland rainforest. A detailed description of the vegetation, climate, fauna and flora of the type locality can be found in Mack (1998).

Figures

FIGURE 1. Idiocnemis lakekamuensis, sp. nov., holotype ♂, Lakekamu basin: habitus.

FIGURE 3. Idiocnemis lakekamuensis sp. nov., holotype ♂, head in dorsal view.

FIGURE 5. Idiocnemis lakekamuensis sp. nov., holotype ♂, Lakekamu: synthorax in right lateral view.

FIGURE 9. Idiocnemis lakekamuensis sp. nov., holotype ♂, Lakekamu: right superior appendage in dorso-lateral view.

FIGURE 11. Idiocnemis lakekamuensis sp. nov., Lakekamu: right superior appendage in dorso-lateral view, SEM.

FIGURE 14. Idiocnemis lakekamuensis sp. nov., ♀, Lakekamu, head in dorsal view.

FIGURE 16. Idiocnemis lakekamuensis sp. nov., ♀, Lakekamu, prothorax in dorsal view.

FIGURE 17. Idiocnemis lakekamuensis sp. nov., ♀, Lakekamu, posterior pronotal lobe in dorsal view.

FIGURE 20. Idiocnemis lakekamuenis sp. nov., ♀, Lakekamu, prothorax in dorsal view, SEM.

FIGURE 21. Idiocnemis lakekamuenis sp. nov., ♀, Lakekamu, posterior pronotal lobe in dorsal view, SEM.

FIGURE 24. Idiocnemis lakekamuensis sp. nov., ♀, Lakekamu, terminal abdominal segments in dorsal view.

FIGURE 28. Known distribution of Idiocnemis lakekamuensis sp. nov. (blue square) and I. milou sp. nov. (red circles) in New Guinea.