Indolestes gracilis expressior ssp. nov. (Kosterin, 2015)

Kosterin, O. E., 2015, Taxonomical notes on Indolestes Fraser, 1922 (Lestidae, Zygoptera). 1. Indolestes gracilis expressior ssp. nov. from eastern Cambodia, IDF-Report 81, pp. 1-11 : 5-9

Indolestes gracilis expressior ssp. nov.

Figure 4 a-h

Material studied

Holotype ♂, Cambodia, Mondulkiri Province, the river upstream Buu Sraa Waterfall, the left bank at the bridge , 12°33'55'' N 107°25'09'' E, 502 m a.s.l., 9 VI 2014; deposited in Naturalis Biodiversity Centre, Leiden, the Netherlands ( RMNH) .

Etymology

Expressions a Latin adjective in gradus comparativus and genus masculinus, meaning ‘more expressed', referring to a more expressed differentiation of the apical part of the cercus than in other subspecies.

Male ( Figure 4 )

Head. Labium bluish in central part, yellowish at margins. Labrum, mandible bases, genae dull bluish ( Figure 4a, b ). Anteclypeus of the same colour with a small indistinct dark spot at centre, postclypeus mostly dark-bronze with anterior part dull bluish forming a central projection of this colour. Frons, vertex and occiput dark-bronze, there is a pair of greenish spots just below lateral ocelli and another one lateroposteriorly of the former. Antennae blackish-brown ( Figure 4b ).

Thorax. Prothorax dull bluish with dorsal suture slightly darker brown and a pair of two indistinct bronze dorso-lateral patches ( Figure 4c ). Posterior lobe slightly raised with smooth margins, light-brown, darker dorsally ( Figure 4a, c ). Mesostigmal plate broadly-triangular, with a transversal lens-shaped central hollow deepening to its lateral ends, and deep middorsal groove. Central hollow and adjacent anterior margin brown, the rest dark-bronze but with brownish lightenings at sides of middorsal groove ( Figure 4c ). Synthorax ground colour changes from olivaceus at mesepisternum to dull blue on sides ( Figure 4a ). There is a broad middorsal dark-bronze band but dorsal ridge narrowly brown. There are elongate black spots at top of humeral and the first lateral sutures and a slight trace of a brownish stripe below mesopleural suture, with a small brown spot with indistinct margins in its dorsal part ( Figure 4d ). Sclerites at wing bases blue. Coxae and trochanters bluish, rest legs brownish, with outer sides of femora, ventral ribs of tibia, tips of tarsi, spines and hooks blackish ( Figure 4a ).

Wings hyaline, major veins dark brown, minor ones black. Discoidal cell very narrow, its dorsal side is ca 0.35 as long as ventral side in fw and ca half as long on hw postnodals 10 on fw, 9 on hw. Pterostigmata of folded fore and hind wings disposed exactly near each other. They are ca 2.2 as long as high, accompanied with two cells below, dark-brown, bordering longitudinal veins somewhat swollen and darkened ( Figure 4e ).

Abdomen. Ground colour dull blue at S1-S3 ( Figure 4a ) changing to brownish at S5- S8 (partly shown in Figure 4f ) but again greyish blue at S9-S10 ( Figure 4g, h ). Tergites 1-7 with solid dark-bronze to blackish dorsal stripes.That on S2 shaped as squid body with a tail directed anteriorly. Those on S2-S7 are constricted anteriorly, before tergite anterior margins, marked with black rings, and rather indistinctly expanding to tergite ventral margins posteriorly ( Figure 4a, f ). S8 dark with indistinct lateral brownish patches in its anterior half ( Figure 4f ). S9 blackish with a pair of indistinct greyish-blue spots at posterior margin, nearly fused to each other, occupying half of its length. S10 greyish blue above changing through reddish-brown to blackish below ( Figure 4h ).

Cerci about twice as long as S10. In dorsal view ( Figure 4h ), their outer outline (bearing sparse robust spines) smoothly curving towards each other to distinct apical portions occupying about 1/3 of the cercus projection to the central axis. Apical portions dropshaped, rounded proximally, bluntly pointed distally, directed caudally but very slightly diverging. Inner outline of cerci elaborate: narrowing at ca 1/5 of their length, then with a ventro-adaxial ledge ending with a long process, then slightly broadening again; cercus apical portion forms a prominent rounded backward ‘heel'. In lateral view ( Figure 4g ), cercus dorsal outline nearly straight at basal 2/3 then bends down. Cercus ventral outline narrowing at basal 1/4, ventro-adaxial ledge with a subbasal blunt spine (not seen in dorsal view) and apical process; cercus apical portion hoof- or pen-like, with a rounded base and attenuated apex, occupies 1/3 of cercus length. Cercus dorsal side greyish blue,apical portion blackish-brown,rest brown ( Figure 4g,h ). Paraprocts light-brown, thrice as short as cerci, rounded in dorsal view, trapezoid in lateral view, their dorsolateral side deeply concave with semicircular ridges occupying the concavities ( Figure 4g, h ).

Measurements [mm] - hw 18; abd (without apps) 29; total length (with apps) 38.

Female unknown

Differential diagnosis and remarks

The shape of the cerci of the new subspecies ( Figure 4h ) is close to that of I. gracilis spp. ( Figure 1 b-e) and I. peregrinus ( Figure 2 ). However, the apical portion of the cerci is curiously inflated basally in dorsal view, forming a prominent ‘heel' protruding medio-anteriorly. So the cerci resemble rather legs and feet of a man in the act of brass swimming than the arms and hands of a man in the act of diving, as in the mentioned species. None of so far described taxa of Indolestes displays this shape of the cercus apical part, modification of which in the new subspecies looks most pronounced as compared to the related taxa. In other subspecies of I. gracilis , I. peregrinus and I. cyaneus , the inner outline of the cercus at the apical portion base in dorsal view just turns caudad without a concavity before the apical part to form the ‘heel'. Drawings of the appendages of I. gracilis spp and I. peregrinus from Ris (1916), Fraser (1933) and Asahina (1976) are reproduced in Figures 1 b-e + 2a-c. Indolestes cyaneus has more robust cerci with a less attenuated and inflated apical part ( Figure 1a ) ( Fraser 1933). The coloration of the cerci, with distinctly darker apical portion, is as in I. peregrinus ( Asahina 1976) , while in I. gracilis gracilis they are almost dark throughout ( Fraser 1933; Asahina 1976). However this character may vary with age, individually and geographically. The paraprocts in /. gracilis expressior ssp. nov. ( Figure 4h ) are bluntly rounded in dorsal view, as should be in I. gracilis .

The body coloration and pattern, with straight margins of the synthorax median black band and the solid abdominal black markings not divided into anterior/posterior or left/ right parts, is similar to those in I. gracilis and contrasted to I. peregrinus ( Asahina 1976) . Moreover, reduction of the humeral spots is similar to the nominotypical subspecies I. g. gracilis from Sri Lanka. Lieftinck (1940) pointed that in that subspecies, these spots are variable from complete absence to 3-4 isolated spots or even fused into irregular fascia (as in I. g. davenporti and I. birmanus ). The small spot below the mesopleural suture in the holotype of I. gracilis expressior ssp. nov. ( Figure 4d ) is brown and diffuse at margins, as it often happens with a variable, environmentally induced melanisation in some damselflies, e.g. in northern populations of Enallagma cyathigerum Charpentier, 1840 in Eurasia ( Kosterin & Zaika 2010).

Yokoi & Souphanthong (2014: fig. 4) provided a drawing of the appendages of a male of « lndolestes sp. 3» ( Figure 5 ) from Paksong, Bolaven Plateau, Champasak Province, southern Laos. Their shape is very similar to I. gracilis expressior ssp. nov., so that specimen most probably represents the same subspecies. Unlike the here described holotype, the photo of the general habitus of this specimen shows a complete humeral stripe (Ibid.: pl. 1). However, the great variation of the humeral pattern is common in Sympecmatinae and observed in I. gracilis gracilis ( Lieftinck, 1940) , hence is expected in Indolestes gracilis expressior as well, perhaps depending on environmental conditions.

Distribution

The subspecies is known from eastern Cambodia and (tentatively) southern Laos.

Habitat

The holotype was startled from a bush branch in a secondary growth at the left bank of the large river which form the well-known Buu Sraa Waterfall. There were also some shallow stagnant pond and pools nearby. This place was at 502 m a.s.l. (as to Google Earth) and was surrounded by countryside but close to the evergreen forest in the river valley downstream of that place. The Laotian male presumably of this new subspecies was collected at 1310 m a.s.l. (Yokoi & Souphanthong 2014).The nominotypical Sri Lankan subspecies inhabits mountains, with localities between 1800 and 2500 m a.s.l. ( Bedjanic et al. 2014: 76-77).

Discussion

I. gracilis sensu lato ranges from Sri Lanka through western (Western Ghats) and southern (Tamil Nadu State) India ( Ris 1916, Fraser 1933), while I. peregrinus ranges from S China to Korea and Japan ( Asahina 1976; Wilson 2009). East Cambodia is situated far to the east from the range of the former and far to the south from the range of the latter. Hence I. gracilis expressior subsp. nov seems to represent the hitherto unknown south-eastern, Indochinese subspecies of this species, characterised by a more elaborated shape of the cerci with a more modified apical part.

No Indolestes spp. have been reported for Vietnam ( Do & Dang 2006). Yokoi & Souphanthong (2014) listed three not identified Indolestes spp. from Laos, with their « lndolestes sp3» most probably representing I. gracilis expressior ssp. nov. Since subspecies is an entity of intraspecies variation, specifically geographical variation, it is undesirable to describe a subspecies by one or two specimens. However, I am quite convinced in existence of this Indochinese taxon because of the unique apical part of the cercus in an area so remote from other subspecies. Of course, further specimens are needed to reveal the variation of the new species and its range and to finally prove its distinctness. Quite likely, it may appear bona species. Note, however, that this was the first and only Indolestes specimen obtained on my five 2-3 week long expeditions to Cambodia in 2010-2014, that is they are very rare. To postpone the description until a consider-able collection accumulates from Cambodia would mean for a long time to operate in discussions of the fauna of Cambodia with an unnamed taxon, among so many others of Indochinese Odonata (e.g. Yokoi & Souphanthong 2014), that is inconvenient.

Figures

Figure 1. Indolestes cf taxa as illustrated in literature - anal appendages, dorsal. - a, I. cyaneus after Fraser (1933: fig. 34, as Ceylonolestes cyanea); - b-d, I. gracilis gracilis: b, after Asahina (1 976: figs. 10, as Indolestes gracilis); c, the type of Lestes gracilis from Hagen's collection (after Asahina 1976: fig. 13, as Indolestes gracilis); d, after Fraser (1933: fig. 28, as Ceylonolestes gracilis). - e, I. gracilis davenporti, after Fraser (1933: fig. 31, as Ceylonolestes davenporti). Not to scale.

Figure 2. Indolestes peregrinus ♂ as illustrated in literature - anal appendages lateral (a), dorsal (b+c). — a,b, after Ris (1916: fig. 2, as Indolestes gracilis perigrinus); c, after Asahina (1976: figs 5, 7). Not to scale .

Figure 4. Details of Indolestes gracilis expression ssp. nov. - a, head, thorax and abdominal segments 1-2; b, head, dorsal view; c, prothorax and synthorax dorsum, dorsal view; d, top of synthorax, lateral view; e, pterostigmata; f, S6-S10 of abdomen; g, anal appendages, lateral view; h, the same, dorsal view. Not to scale.

Figure 5. Male anal appendages, dorsal. - Indolestes?gracilis expressior ♂ ssp. nov. after Yokoi & Southpanthong (2014: fig. 4, as Indolestes sp. 3).