Drepanosticta adenani, Dow & Reels, 2018

Dow, Rory A. & Reels, Graham T., 2018, Drepanosticta adenani sp. nov., from the Lanjak Entimau Wildlife Sanctuary in Sarawak (Odonata: Zygoptera: Platystictidae), Zootaxa 4379 (3), pp. 429-435 : 430-434

Drepanosticta adenani sp. nov.

( Figs. 1 – 15 )

Holotype. 1 ♂ ( SAR16 _ PST11 ), seepage at head of second order tributary to Sungai Jela, Lanjak Entimau Wildlife Sanctuary, Ulu Engkari, Sri Aman Division , Sarawak, Malaysian Borneo, 1.4343N, 111.9987E, ca 440m a.s.l., 18 vii 2016, leg. R.A. Dow, deposited in the Natural History Museum, London ( BMNH).

Paratypes. 1 ♀ ( SAR16 _ PST12 ), location and date as holotype, leg. G.T. Reels, to be deposited in the Natural History Museum, London ; 2 ♂♂ ( SAR17 _PST35, 36), 1 ♀ ( SAR17 _PST37), 1 teneral ♀ ( SAR17 _PST38), seepage at head of second order tributary to Sungai Datai, Nanga Bloh, same wildlife sanctuary but Kapit Division, 1.6532N, 112.2729E, ca 185m a.s.l., 31 x 2017, leg. R.A. Dow, 1 ♂ to be deposited in the Sarawak Museum, Kuching.

Etymology. The species epithet adenani , a noun in the genitive case, is a dedication to the late Tan Sri Adenan bin Satem (27 January 1944 – 11 January 2017), Chief Minister of Sarawak from 2014–2017, in recognition of his support for biodiversity research and conservation in Sarawak, and for starting the Research for Intensified Management of Bio-rich Areas (RIMBA) project, which includes LEWS.

Description of holotype. Head ( Fig. 1 ). Labium pale brownish except darker end hooks. Labrum pale yellow, narrowly black along free margin. Mandible bases pale yellow, black along lower margin. Anteclypeus pale yellow, postclypeus shining black. Vertex, frons and occiput bronzy black, underside of head shining black. Ratio of width of compound eye to width of vertex measured at level of lateral ocelli ca 0.7. Transverse occipital carina prominent. Ocelli whitish. Antenna with scape black, whitish at top, pedicel black and pale brown, right flagella black, left missing.

Thorax. Prothorax almost entirely chestnut brown. Posterior pronotal lobe ( Figs 3 , 6 ) short, with free corners almost right-angled, slightly folded up, pair of short, flattened horns inwards of these, but still widely separated, nearly triangular when viewed from rear, slightly curved forwards. Area behind and in between horns bronzy black. Synthorax ( Fig. 6 ): Mesepisternum and antealar triangles entirely bronzy black. Mesepimeron and metepisternum almost entirely chestnut brown, becoming paler above metakatepisternum. Upper part mesokatepisternum chestnut brown, becoming paler towards coxa. Metepimeron yellowish with brown area below metepleural suture, expanded near antealar carina. Metakatepisternum and venter of synthorax yellowish. Legs (right anterior leg absent below trochanter): each with coxa and trochanter yellowish, femur yellowish with faint, poorly defined dark streaks on extensor and flexor surfaces, dark for short distance above joint with tibia. Tibia brown with obscure darker patches, tarsi with small black marks at segment joints, claws pale brown. Wings: 14 Px in Fw, 14 (left) or 12 (right) in Hw. Basal Ax slanted in all wings. Vein Ab present, joined to Ac to form Y with short stalk. Arculus slightly distal to Ax2. R4 arising just distal to subnodus in Fw, at subnodus in Hw, IR3 joined to it by a short stalk. Pterostigma trapezoidal with costal side shorter than anal side, brown with narrow pale border, covering slightly more than one underlying cell.

Abdomen. S1 brown, becoming pale lower laterally. S2 dark brown above and laterally apically, paler brown basally laterally, margin of tergite pale. S3–7 largely very dark brown to black, with broad basal whitish markings becoming brown centrally dorsally. S8 similar but basal marking not reaching dorsum and extended along lower margin. S9–10 ( Figs 8, 10 ) brown and black laterally, blue above; S9 with deflated appearance dorsally. Anal appendages ( Figs 12–14 ): cerci brown, in lateral view broad at base, rapidly narrowing, upper margin running ca straight to rounded apex, lower margin sinuous ( Fig. 13 ). In dorsal view ( Fig. 12 ) short, sharp pointed, interior projection at ca one-third length, narrowing immediately after this, somewhat hollowed on inner surface. Paraprocts pale but darkening towards tips, simple, lacking spines or projections ( Figs 13, 14 ). In lateral view ( Fig. 13 ) tapering from broad base, turned slightly down and inward apically, apices directed upwards, in ventral view ( Fig. 14 ) apices appearing rounded.

Genital ligula. Terminal segment narrower than penultimate segment, apically widened and divided into two arms lying on either side of shaft ( Fig. 15 ), these expanded and turned through almost a right angle at ends, so apices pointed toward thorax and slightly down. Internal fold wide, clearly visible in ventral view.

Measurements (mm). Abdomen without anal appendages 33, cercus ca 1, Hw 21.5.

Female. Overall very similar to male, except as noted below. Head ( Fig. 2 ). Labium paler than in male.

Thorax. Prothorax with corners of posterior pronotal lobe produced to rear ( Figs 4, 5 , 7 ), horns slightly shorter than in male, upright ( Fig. 4 ). Wings with R4 at subnodus except in right Fw, where slightly distal to subnodus, 12 Px in Fw, 11 Px in Hw. Pt orangey brown.

Abdomen ( Figs 9, 11 ). S8 brown above, whitish lower laterally and most of sternum, except narrow dark central longitudinal streak. S9 brown basally and lower laterally, remainder blue. S10 short, blue above, pale lower laterally. Cerci about same length as S10, triangular in lateral view. Ovipositor extending further than tips of cerci by their own length, dark brown and pale, styles (broken) dark brown.

Measurements (mm). Abdomen without anal appendages or ovipositor 29.5, Hw 21.5.

Variation in paratypes. Males. There is little variation in markings, none significant. The exact shape of the sinuous lower margin of the cerci in lateral view shows some small variation. S9 is not depressed on the larger specimen but is on the smaller, the horns on the posterior pronotal lobe are shorter in the same specimen and in the Hw only Ac is present There is significant variation in size between the paratypes (see below), which are both smaller than the holotype. Females. One of the female paratypes is teneral and although recognisably this species, is of no use for measurements and vein counts. The other is mature, and the pale colour on the labrum is reduced compared to the female described, and bluish. The corners of the posterior pronotal lobe are only slightly produced to the rear, the horns are slightly longer (relative to the rest of the posterior pronotal lobe) than in the female described, and slightly curved forwards. The cerci are a little longer than S10.

Measurements (mm). Males: 12 Ax in Fw, 11 in Hw, Abdomen without anal appendages 29–32, Hw 18.5–20. Female: 13 Px in Fw, 12 in Hw, abdomen without anal appendages or ovipositor 29, Hw 20.5.

Diagnosis. The male is easily separated from its known congeners in Borneo except D. forficula , by the extremely simple form of its paraprocts, lacking any spines or projections, and tapering to tip. It is separated from D. forficula by the paraprocts lacking a sharp turn around mid-length. Both sexes are separated from all other Drepanosticta species known from Borneo by the form of the posterior pronotal lobe, with a pair of short erect and flattened horns positioned slightly in from the free corners. Where a pair of upright horns are present on the posterior pronotal lobe in other species they differ in form, and the species in question is either considerably smaller or has antehumeral markings.

Remarks. The females are associated with the male by reasonable supposition; that from the same location as the holotype was found in the same seepage as the male, and is closely similar in colouration and the structure of the posterior pronotal lobe. The females from the second location were found within a metre of the males. The holotype was found perched at around head height on vegetation at the side of a short arm of the seepage, the female was in a separate, darker, arm of the same seepage. The male paratypes were perching close to a bank at the extreme head of the seepage, at about waist height, and were very inconspicuous. The locality at Sungai Jela is located in pristine or near pristine mixed dipterocarp forest, the other location is in forest with a history of disturbance for local use, but there was no sign of disturbance around the stream where the species was found.

The relationships of Drepanosticta adenani to other species known from Borneo or beyond are not clear. Considering only species from Borneo, it shares extremely simple paraprocts and simple cerci with D. forficula , and despite the different shape of the posterior lobe of the prothorax, lacking in D. forficula , it may be closest to that species. The deflated appearance of S 9 in the holotype and one of the male paratypes, whilst undoubtedly largely an artefact caused by drying, is curious because such artefacts are common in D. forficula and D. sbong (see Dow (2010: 65–66); D. sbong is another species that is difficult to place), but much less so in other members of the Bornean Platystictidae . Further discussion of the relationships of D. adenani would be premature and merely speculative.

Together with Telosticta iban Dow, 2014 and Elattoneura mauros Dow, Choong & Ng, 2010 , Drepanosticta adenani is the third species of damselfly to be described from Lanjak Entimau. None of these species has yet been found outside of the wildlife sanctuary, illustrating the importance of this area for biodiversity conservation in Sarawak.

Figures

FIGURES 1–2. Drepanosticta adenani sp. nov.: (1) Holotype male, head dorsal-frontal view; (2) paratype female (SAR16_PST12), head dorsal-frontal view.

FIGURES 3–5. Drepanosticta adenani sp. nov., posterior pronotal lobe: (3) holotype male, lateral (right side, flipped to left) view, scale bar 0.2mm; (4) paratype female (SAR16_PST12), lateral view, scale bar 0.2mm; (5) paratype female (SAR16_PST12), dorsal view, scale bar 0.5mm.

FIGURES 6–11. Drepanosticta adenani sp. nov., synthorax in lateral view: (6) holotype male; (7) paratype female (SAR16_PST12). Markings of terminal abdominal segments: (8) holotype male, lateral view; (9) paratype female (SAR16_PST12), lateral view; (10) holotype male, dorsal view; (11) paratype female (SAR16_PST12), dorsal view.

FIGURES12–15. Drepanosticta adenani sp. nov., anal appendages andgenital ligulaof holotype male: (12) anal appendages, dorsal view, scale bar 0.5mm; (13) anal appendages, lateral view, scale bar 0.5mm; (14) left paraproct, ventral view, scale bar 0.5mm; (15) genital ligula, ventral view, scale bar 0.2mm.