A review of the genus Bornargiolestes Kimmins , 1936 ( Odonata : Zygoptera ) with a description of two new species from Sarawak , Malaysia

Acknowledgements: Collecting in Sarawak was conducted by permission of the Sarawak Forestry Department (SFD) and Sarawak Forestry Corporation (SFC); thanks are due to all of the SFD and SFC staff that have assisted me. Graham Reels took part in much of the fieldwork during which Bornargiolestes specimens were collected, and collected some of the material used in this paper. Vincent Kalkman pointed out the existence of an additional specimen probably of B. nigra in RMNH and provided useful discussion on the genus and its allies. Albert Orr provided information on his Bornargiolestes specimen from Brunei, useful discussion and a valuable review of the manuscript, which greatly improved it. David Goodger and Benjamin Price provided considerable assistance at BMNH; in particular Benjamin Price made photographs of the wings and thorax of B. nigra that were used to make the figures presented here. Luke Southwell and Walter Kebing collected specimens used in this paper, and Luke Southwell was vital to the organisation of fieldwork in the mid Baram area of Sarawak. The abstract was translated into Bahasa Melayu by Chee Yen Choong. Fieldwork in the mid Baram area in 2009 was partly supported by a grant from the Worldwide Dragonfly Association. Fieldwork on Gunung Penrissen in 2009 and at Lanjak Entimau Wildlife Sanctuary in 2013 was supported by grants from the International Dragonfly Fund. Images 10 and 11 were made with the aid of DIVA GIS. Abstract: The poorly known genus Bornargiolestes is reviewed and a fresh diagnosis is provided. Two new species, Bornargiolestes fuscus and Bornargiolestes reelsi are described. Illustrations, distribution maps and a key to the males of the genus are given.


INTRODUCTION
The genus Bornargiolestes was erected by Kimmins (1936) for B. nigra Kimmins, 1936. B. nigra was known only from the holotype male, from Mount Dulit in Sarawak, and no other specimen from the genus was reported until Orr (2001) recorded a teneral male of a Bornargiolestes species, of uncertain status, from Brunei.Subsequently Dow & Reels (2009) recorded a Bornargiolestes species from Mount Dulit, which they considered a different species from B. nigra.The genus was also recorded from Kubah National Park in western Sarawak, and Lambir Hills National Park in northeastern Sarawak (Dow & Reels 2010), from Gunung Penrissen in western Sarawak Dow (2012), and from Mount Singgai, also in western Sarawak (Dow & Reels 2013).Additionally, V.J. Kalkman also found an old specimen from Kalimantan in the collections of the Naturalis Biodiversity Centre.However, all the recent material from Sarawak and Brunei belongs not to B. nigra, but to two previously undescribed species, with only the specimen from Kalimantan probably representing true B. nigra; this species appears to be an exceptionally elusive insect.The current family placement of the genus is uncertain, as it has traditionally been placed in the Megapodagrionidae, a family now considered polyphyletic (Dijkstra et al. 2013a).Dijkstra et al. (2013b) left Bornargiolestes as incertae sedis (the course followed here) but noted it could possibly be included in the Thaumatoneuridae.
The new species are described here as Bornargiolestes fuscus sp.nov.and Bornargiolestes reelsi sp.nov.With the material now available a better characterisation of the genus is possible; this is given below.
Terminology used here for wing venation and male abdominal terminalia follows that in Watson & O'Farrell (1991); other terminology mostly follows Westfall & May (1996).The acronyms BMNH and RMNH are used below for the Natural History Museum, London and the Naturalis Biodiversity Centre, Leiden.All material at least initially in the author's collection has been given a reference code which is stated here.All figures and images made by the author unless otherwise noted in the caption.

Diagnosis
A genus of medium-sized, predominantly brown to black damselflies with short legs, distinguished from all genera presently or formerly placed in the Megapodagrionidae s.l. by the following combination of characters.Prothorax with middle pronotal lobe produced into spurs or projections in lateral posterior part and bearing a pair of dorsal depressions on either side.Posterior femur not reaching the first abdominal segment when folded back against the synthorax.Long wings (held closed in life) petiolate to beyond the base of the quadrilateral and the nodus situated at about one quarter of the length of the wing from the base.Arculus at or slightly distal to Ax 2. R 4 arising at or very close to Sn, IR 3 1-4 cells distal to Sn, quadrilateral long: in Hw anal-distal corner at or only slightly before level of nodus.Seminal vesicle inflated and flask shaped.Shaft of penis bearing long dense setae.Terminal segment of penis with pair of apical arms, directed dorsally and basally, the ends of these expanded and flattened.Superior anal appendages of male 2-3 times the length of S10, dorso-ventrally expanded at ca 1/3 to 1/2 length, at least weakly cleft at tip.Male inferior appendages broad at base but narrowing rapidly to a long slender tip about half the length of superior appendages.Kimmins (1936) emphasised wing venation characters in his description of Bornargiolestes, but omitted some other interesting structural characters.In all species the middle pronotal lobe has its lateral posterior parts produced into rounded projections bearing denticles (Images 3-5), and also has a pair of depressions on either side on its dorsal surface: one at the base of the lateral projection and the other more dorsally positioned (marked in Image 5).However both of these characters, especially the depressions, are less pronounced in the genotype than in the new species described here.Kimmins noted the similarity of Bornargiolestes to Burmargiolestes Kennedy, 1925, a genus which also has a pair of depressions on either side of the dorsum of the middle pronotal lobe, but lacks the lateral projections (Image 6 shows the prothorax of Burmargiolestes laidlawi Fraser, specimen from BMNH).The legs are missing in the holotype of B. nigra, so it is possible that they are longer than stated in the diagnosis above; in the teneral male from Kalimantan treated as B. nigra here they conform with the diagnosis.

Remarks
Diagnostic features of the male anal appendages are best seen in lateral and ventral views, dorsal views are of little value in distinguishing species; for this reason only lateral and ventral views are given in the illustrations.The reader is referred to Kimmins (1936: fig. 9B) for a dorsal view of the anal appendages of B. nigra.The branches defined by the cleft tips of the superior anal appendages are referred to as the subapical branch (the interior branch in ventral view) and the apical branch.

Etymology
Fuscus, a Latin adjective, meaning brown.

Description of holotype male
Head: Labium pale.Labrum, mandible bases, genae and anteclypeus mostly whitish, postclypeus with central third brown, pale laterally.Frons, vertex and occiput black and dark brown, with a short yellowish streak reaching from each lateral ocellus towards the rear of, but not touching, the antenna sockets.A yellow streak on antenna bases, scape and pedicel pale and brown, flagella missing.
Thorax: Prothorax pale brown with indistinct darker areas.In dorsal view lateral posterior part of the middle pronotal lobe bulging outwards (as in Image 3, which shows a female paratype) rather abruptly as a sub-triangular blackish projection bearing denticles, protruding well beyond the propleuron, above this projection a shallow lateral depression and another depression placed dorsally.Synthorax brown (reddishbrown in life), becoming pale yellowish on lower part of metepimeron and on venter.Legs almost entirely pale brown.Posterior tibia approximately as long as the mesopleural suture measured from antealar carina to corner of mesinfraepisternum, posterior femur shorter, not reaching first abdominal segment.-Wings: hyaline, R 4 arising just distal to Sn, IR 3 2 cells distal.20 Px in Fw, 18 (left) or 17 (right) Px in Hw.Pterostigma brown, with incomplete and poorly defined pale border, approximately trapezoidal, covering one central underlying cell and parts of the cell on either side.The anal side is thickened relative to the other sides and surrounding veins.
Abdomen: Brown and yellowish.S1 yellowishbrown laterally, brown above.S2 mostly brown.S3 brown above, mostly yellowish laterally but entire apical sixth dark brown and the yellowish coloration intruding dorsally basally and subapically, the same pattern repeated on S4-6, with the brown becoming darker on successive segments.S7 without the subapical dorsal pale area, S8 dark brown except for yellow patches basal laterally and along the lower margin of the tergite.S9-10 entirely very dark brown or black.S9 expanded moderately from base in dorsal view, S10 maintaining the same width.In lateral view S8 and S9 expanded, reaching greatest height at the junction of the segments, narrowing quite abruptly from about 1/3 length S9.S9 with a basal diamond-shaped pit on the dorsal midline (Image 8).Penis (Fig. 5) typical for genus.Superior anal appendages shaped as in (Figs. 7,10), mostly pale, with the subapical branch of the tip of the superior appendage well developed (Fig. 10).Inferior appendages mostly dark, with pale tips to the spine, which is slightly bulbous apically just before tip where it narrows rather abruptly to a point.
Description of female paratype (SAR07_8_MEG3, as male except as noted) Thorax: Wings: 3 Ax except right Fw where 2 Ax.24 (left) or 21 (right) Px in Fw, 20 (left) or 21 (right) in Hw.R 4 arising at subnodus in right Fw. Wing margin contracted slightly at proximal end of pterostigma, which variably covering slightly less than two to parts of three underlying cells.
Abdomen: Colouration very similar to male.No depression or split in dorsum of S9.Superior anal appendages just longer than S10, conical and roundly pointed.Ovipositor brown, reaching ca the level of the tips of the superior anal appendages, valves with only minute teeth along lower edge.
Variation: In some individuals, including all from Lambir Hills, the clypeus is entirely or almost entirely pale, but in the females from Dulit and the mid Baram the pale lateral marks on the postclypeus are darker and less distinct.One male from Gunung Mulu has a much darker thorax than any of the others, and dark tibae and tarsi; presumably this is a very mature individual.The pit on S9 of males varies in size but is present on all available specimens.Mature females from Dulit, the mid Baram and Lanjak Entimau in western Kapit have the mesepisternum and mesepimeron darker than in females from Lambir and Mulu.In both sexes R 4 variably arises slightly proximal, at, or slightly distal to Sn.In specimens from Mulu and the mid Baram IR 3 arises 2 cells distal to Sn, but in specimens from Lambir it typically arises 3 cells distal to Sn, occasionally 4 cells distal and in the female from Mount Dulit it arises 2.5-3 cells distal.In some individuals (e.g. the female described) there are 3 Ax in some wings.The colour of the pterostigma is darker in many individuals, but paler in teneral and semi-teneral specimens.In some individuals the wing margin is contracted slightly at the proximal end of the pterostigma (as in Figs 3, 4, which show a paratype of B. reelsi).
Measurements of the holotype and the female taken in tandem with it were strongly red brown in life.Males from the mid Baram, Lanjak Entimau and in particular Mount Dulit, are lacking and there is a difference in the darkness of the upper part of the synthorax of females from these locations, but they agree more in wing venation and structure of the pronotum with B. fuscus sp.nov.males rather than with B. nigra and are considered to belong to the former species in the absence of more convincing evidence to the contrary.Orr ( 2001) treated the male from Brunei as of "uncertain status".Later Orr (personal communication 2013) compared that specimen against the description and images of B. fuscus provided by this author and confirmed its identity.

Remarks
The male from Kalimantan Barat is teneral, but the ends of the superior anal appendages are intact and agree well with the holotype (shown in Figs. 17,20).This specimen also agrees well with the holotype in size (Hw 28mm, abdomen without anal appendages 38.5mm), most details of wing venation, coloration of the labrum, clypeus and mandible bases, and the size and shape of the lateral projections on the rear part of the median pronotal lobe (Image 4).Overall the specimen is brown, and as it is teneral, it is likely to be substantially paler than it would be if mature.IR 3 arises two cells distal to Sn in all wings except the right Fw, where it arises one cell distal to Sn.The quadrilateral is short (compared to the two new species) in both wings, with the anal-distal angle falling short of the nodus; in the holotype this is the case in the Fw, but not in the Hw.A note on the pin indicates that Lieftinck had compared it with the type of B. nigra and considered it conspecific.I provisionally agree with Lieftinck's opinion, but see the discussion of the penis below.
The legs of the holotype of B. nigra were missing even when Kimmins wrote his description of it.The femur and tibia of four of the legs are still present in the Kalimantan male, the posterior femur is relatively longer than that of B. fuscus sp.nov.and B. reelsi but still not quite long enough to reach the first abdominal segment; the posterior tibia is significantly longer than the mesopleural suture measured from antealar carina to corner of mesinfraepisternum, in contrast to the other two species.
The penis of the holotype is mounted in Canada balsam on a card on the pin, but is hardly visible and appears compressed and damaged; it is not possible to check the accuracy of Kimmins' illustrations (Kimmins 1936: Fig. 9C, D).If Kimmins' illustrations (one of which is reproduced in slightly modified form in Fig. 6) is accurate, the penis of B. nigra has a broader terminal segment, with shorter apical arms, than either of the species described here.Given the fragile condition of the male from Kalimantan it was thought better not to attempt the extraction of its penis, however the penis is partly visible and appears to have a much narrower terminal segment than shown in Kimmins' illustration, creating some doubt over its status.
Both the holotype and the specimen from Kalimantan Barat lack the pit on the dorsum of S9 that is present on the males of the other two species.

Description of holotype male
Head: Labium mostly pale, except laterally and around free edge of post mentum.Labrum bluish.Mandible bases mostly pale.Anteclypeus mostly dark brown.Genae mostly black, except immediately adjacent to mandible bases.Postclypeus, frons, vertex and occiput black, with a yellowish streak reaching from each lateral ocellus towards, but not touching, the antenna sockets.Antennae with scape brown, pale at top, pedicel brown, flagellum black.
Thorax: Pronotum with anterior lobe brown, dark laterally and on anterior carina, middle and posterior lobes black.Lateral posterior part of the middle lobe produced outwards (Image 5) as a rounded projection bearing a few denticles, protruding well beyond the propleuron in dorsal view, above this projection a small depression and another larger depression placed more dorsally (Image 5).Propleuron black.Synthorax almost entirely black, except venter which is pale, and some brown patches near the antealar carina and the coxae.A distinct peak is present on the antealar Abdomen: Mostly black.S2-7 with a narrow incomplete pale basal annulus expanded on the lower lateral part of the tergite, where continued narrowly along the margin for most of the length.S8 almost entirely black, S9-10 black.In dorsal view S9 expanded from base, S10 maintaining the same width, S9 with a small, shallow basal diamond shaped pit on the midline (Image 9).Penis very similar to that of B. fuscus sp.nov.Superior anal appendages shaped as in (Figs. 9, 12), black basally, pale on the upper and internal surfaces distally, the subapical branch of the cleft tip barely developed, so hardly visible in ventral view (Fig. 12).Inferior appendages mostly black.
Variation in paratypes: Immature individuals are paler than the holotype and described female paratype.In both sexes R 4 typically arises at or slightly proximal to Sn, but occasionally arises very slightly distal to it, IR 3 arises 2-3 cells distal to Sn.The pit on the dorsum of S9 is present in all males examined, but is very small in some individuals.
Remark: The habitus of one of the paratypes is shown in Image 2. The contrasting coloration of femur and tibia (Image 2) in mature males of B. reelsi sp.nov., with femur pale and tibia dark is readily apparent in specimens and should certainly assist in distinguishing them from superficially similar looking Devadatta species, with which it can co-occur, in the field.However, the coloration of femur and tibia appears much more similar in immature males and females, so limiting the value of this character.

DISCUSSION
The two species described here, B. fuscus sp.nov.and B. reelsi sp.nov., appear more closely related to each other than to B. nigra.They share greater development of the structures of the middle pronotal lobe than B. nigra, very similar wing venation and penis structure and both bear pits on the dorsum of abdominal S9, lacking in B. nigra.Judging from the specimen from Kalimantan Barat provisionally considered as B. nigra, the two new species also have shorter legs.
Bornargiolestes remains a poorly known and elusive genus, its habitats are barely understood, its larva is unknown and the type species is still known only from two old specimens.The genus is associated with steep forested terrain, where a substantial proportion of the available specimens of B. fuscus sp.nov.and B. reelsi sp.nov.have been taken on trails.Where the individuals have been found at water, they have often been found at permanently wet cliff faces deep in forest, or at very small trickles and seepages beside small streams.These habitats are characterised by having only the barest amount of water running above the leaf litter; in some cases no flow was visible above the leaf litter.Nothing whatsoever has been recorded on the habitat of B. nigra, but the type was collected on the Tinjar (eastern) face of Mount Dulit, which is almost entirely steep to extremely steep.Attempts to find the larva of B. fuscus sp.nov.and B. reelsi sp.nov. at sites where freshly emerged individuals have been found have so far yielded no results.B. fuscus sp.nov.has been found at altitudes from close to sea-level up to at least 900m; B. reelsi sp.nov.has been found from close to sea-level up to ca. 1100m.The type of B. nigra was collected at around 900m; the altitude at which the specimen from Kalimantan Barat was collected is not given on the labels, and the height of Mount Liang Kubung is unclear.Most locations where B. fuscus has been found are intact primary forest, but the habitats in the mid Baram area and on Mount Dulit have been disturbed by logging.Similarly, some of the habitat on Gunung Penrissen where B. reelsi has been found has been disturbed by logging in the past.Habitats such as described above are common over much of Borneo, but Bornargiolestes has been found only at a small percentage of apparently suitable sites surveyed; clearly the species of this genus are very local in occurrence and our understanding of their habitat requirements is inadequate.