treatment provided by
Amphicnemis valentini , sp. nov.
Amphicnemis gracilis Krüger, 1898 — Do et al. 2011: 55, Photo 4—Report from Phú Quốc Island.
Type material. Holotype: ♂ ( Fig. 3a View Figure ), Cambodia, Preah Sihanouk Province, Ream Peninsula , lower reaches of a rivulet in lowland evergreen forest, 10.52258 N 103.69556 E, 16 m a.s.l., 5 iii 2017, O.K. leg.; deposited in Naturalis Biodiversity Centre, Leiden, the Netherlands ( RMNHAbout RMNH)GoogleMaps . Paratypes: 1 ♂ (preserved in alcohol), the same place, 10.5238 N 103.6955 E, 20 m a.s.l., 4 iii 2017, N.V. Priydak leg.; 1 ♂, 1 ♀ ( Fig. 3b View Figure ), the same place, 10.5226- 5238 N 103.6955 E, 16-20 m a.s.l., 5 iii 2017, O.K. leg.; 4 ♂♂, 6 ♀♀ (5 mature, 1 immature), Vietnam, Kiên Giang Province, Phú Qu ốc Island , 10.251 N 104.029 E, 20 viii 2016, T.K. leg.GoogleMaps
Additional data: visual and photographic records. 1 ♂ (a photo, Fig. 1a View Figure ), the type locality, 10.5238 N 103.6955 E, 4 iii 2017, O.K. 10 ♂♂, 13♀♀ (photos, Figs 1-2View FIGURE 1View FIGURE 2), Vietnam, Kiên Giang Province, Phú Qu ốc Island, 10.251 N 104.029 E, 19-20 viii 2016, T.K. 1 immature ♀ (a photo)GoogleMaps , Cambodia, Koh Kong Province, Tatai Commune , a lower course of an unnamed tributary of the Tatai Riverestuary, 11.5186 N 103.1233 E, 9 xii 2017, Gerard Chartier.GoogleMaps
Etymology. The specific name, a noun in genitive case, is derived from the name of O.K.’s son Valentin, who, at the age of six, accompanied his parents at the type locality when they found this species.
Head ( Fig. 4e View Figure ) mostly metallic black, dorsal side with a green shine, face with some yellowish markings as follows: Labium yellowish. Labrum glittering black shading to yellowish on lower one-third. Mandible bases yellowish along sides, brownish in middle (border of colour indistinct). Vertical surface of clypeus saturated yellow below, dark-brown above. The border of these colours, looking like a pair of fused broadly triangular spots, mostly coincides with the wavy suture on the vertical surface of the clypeus, but laterally the yellow colour extends above it. Horizontal surface of clypeus glittering black. Genae dull greenish below, brownish-black above, dull greenish colour extending dorsally along margins of compound eyes and alongside clypeus towards antefrons ( Fig. 4e View Figure ). Ventral half of antefrons dull greenish-yellow (only narrowly so towards middle), dorsal half black with a pair of large dull greenish spots immediately below antenna bases. Antennae blackish-brown, but apex of segment 1 and anterior part of segment 2 yellowish. Occiput with long golden bristles. Compound eyes in life ( Fig. 1 View Figure ) greenish brown above, gradually turning yellowish green below; darker upper part with a narrow greenish rim along margin.
Thorax. Prothorax ( Fig. 4c–d View Figure ) metallic black with variable metallic gloss above, yellowish below (border between the two colours indistinct). Anterior lobe with a rounded margin, brown at sides, black with a green shine at middle, and with large roundish dorsal markings of yellowish colour laterally on either side ( Fig. 4c View Figure ). Medial lobe black with a bluish-green shine on its proximal two-thirds and bronze-green shine on its distal third; posterior lobe black with a strong violet shine ( Fig. 4d View Figure ). Posterior lobe produced into a robust and long hook-like process ( Fig. 4c View Figure ) generally inclined to the left side ( Fig. 4d View Figure ) and evenly curving anteriorly so that its tip is nearly horizontal ( Fig. 4c View Figure ), its margins rough. Distance from anterior lobe base to process tip slightly less than median lobe length. Lateral posterior extremities of posterior lobe bluntly angulated ( Fig. 4c View Figure ). In dorsal view ( Fig. 4d View Figure ), posterior lobe margins are broadly and evenly concave at sides and more narrowly and pointedly concave at center, so that its outline resembles a bow composed of two horns. Mesostigmal plate easily observed from above ( Fig. 4d View Figure ), of the typical male coenagrionid form, as composed by a pair of transverse hollowed parts, long triangular with slightly convex margins in outline, brownish with a green shine, and two slightly semicircular anterior ridges at middorsal suture. Synthorax ( Fig. 4a View Figure ) glittering bronze-black (with mixed purple and green shine) dorsally, yellowish ventrally, the transition rather indistinct, with an uneven border and transitioning through brown over the middle of mesinfraepisternum (where black projects unevenly ventrally) through spiracle to ventroposterior corner of metepisternum. Dorsoposterior part of metapleural suture with a blackish-brown darkening connecting through vague brownish spots at posterior part of metepimeron to black dorsum of synthorax; posterior ridge of metepimeron brownish-black. Pleural sclerites brown, some with a greenish shine. Venter of synthorax yellowish.
Legs ( Figs 3a View Figure , 4a View Figure ) yellowish with blackish brown parts as follows: stripes along extensor surface of femora (not extending to both ends of metafemora), apices of femora, bases of tibia (markedly at protibia), all segment joints of tarsi; spines blackish-brown, claws brown with black apices.
Wings hyaline; venation blackish-brown; 13 (left) - 14 (right) Px in FW, 11 (left) - 12 (right) in HW. Arculus noticeably distal to Ax2. 1A arising at level of arculus. IR3 and R4 arising distal of subnodus. Pterostigmata ( Fig. 4b View Figure ) similar in both wings, brownish-black, with a lighter margin, costal side shorter than anal side, which is slightly shorter than underlying cell; both transversal sides convex, proximal one slanting, distal one perpendicular; ventral margin thickened.
Abdomen ( Fig. 3a View Figure ) with tergites brownish-black dorsally (S1–2 with a green shine, Fig. 4a View Figure ), yellowish ventrally; border of colors distinct on S1–2 and S10, but indistinct on S3–9. S1–7 tergites with indistinctly darkened apices, so that dark colour extends to ventral sides and becomes more saturated-black on dorsum, and indistinctly lightened bases, so that yellowish-grey colour extends dorsally; there is also some lightening proximally of apical darkened parts. S10 tergite cream white with a large triangular dorsal brown spot with indistinct borders; appendages cream white. All sternites yellowish. S10 posterior margin with a small, almost rectangular central projection.
Cercus bifurcate, its dorsal branch moderately curved down in lateral view ( Figs 5a View Figure , 7e View Figure ), with a slightly convex dorsal margin and convex for proximal two-thirds of ventral margin while distal third very slightly convex so that dorsal branch expands in its distal half; apex bluntly rounded. In dorsal view ( Figs 5b View Figure , 7f View Figure ), dorsal branches in general look similar to their lateral view, gradually curving towards each other, their outer margins convex, proximal two-thirds of inner margin concave, especially in middle third; distal third of inner margin very slightly convex, apices bluntly rounded. A small process of dorsal branch of cercus at ca one-fourth of its length, directed up and inside, visible in both dorsal and lateral view ( Figs 5a–b View Figure , 7e–f View Figure ) and looking bigger and blunter in dorsal view. Ventral branches of cerci 0.6 times as long as dorsal branches, in ventral ( Figs 5a View Figure , 7e View Figure ) and dorsal ( Figs 5b View Figure . 7f View Figure ) views narrow, slightly tapering but with expanded apices truncated at ca 45° to body axis, with very slightly concave, almost straight posterioadaxial margins, dorsally with black sclerotised ridges. In lateral view ( Figs 5a View Figure , 7e View Figure ), ventral branch narrows considerably to a ‘neck’ just before apex, which expands in a long triangular manner, with a rounded ventral angle, acute dorsoposterior angle and straight ventroposterior margin. Paraprocts very short, bluntly triangular with rounded apices as seen in ventral view ( Figs. 5c View Figure . 7f View Figure ).
Genital valves ( Fig. 4f View Figure ) leafy, touching each other with their convex inner margins, with triangularly pointed posterior projections at level of segment joint, and an expanded lateroposterior margin.
Measurements (in mm). Abdomen without appendages 33; HW 19; total length 40.
Variation in males scarce ( Fig. 1 View Figure ). The HW length 18–21 mm, the number of FW Px 11–14. Total length 39– 41 mm, abdomen without appendages 31–33 mm. In one Cambodian male paratype the prothoracic horn is strongly inclined to the left side as in the holotype (perhaps just individual deviations of this long and thin structure) and is broken in the other, but is directed perfectly ahead in all Phú Quốc paratypes.
Resembles male but ca 15% larger (but abdomen only ca 12% longer), and with different colouration of thorax and abdomen tip.
Head ( Fig. 6e View Figure ) mostly glossy black, its dorsal side with a strong purple lustre at sides of ocellar bulge and two patches of strong bluish-green lustre near compound eyes; face black with some pale markings. Labium yellowish. Lower half of labrum yellowish, upper one black, the latter colour extending to middle of labrum centrally, but to four-fifth laterally; border of colour indistinct. Mandible bases yellowish with large, somewhat indistinct, rounded brown spots centrally. Clypeus coloured as in male. Genae greenish below, brownish-black above, with greenish colour extending dorsally along compound eye margins and towards anteclypeus, bordering narrowly triangular downward projections of black colour. Antefrons mostly greenish, its dorsal part black, border of colours distinct and wavy; below antenna bases there is a pair of rounded trapezoid greenish spots; remainder of postfrons black. Antennae blackish-brown but anterior parts of segments 1 and 2 and apex of segment 2 yellowish. Occiput with long light-brown bristles and a short yellowish-brown streak along occipital ridge. Eyes in life saturated bluishgreen, above changing to darker olive-green, yellowish-green in the dried specimen.
Thorax. Prothorax ( Fig. 6c–d View Figure ) entirely light bluish-green when alive, greenish-brown in the dried specimen; posterior lobe with a long central horn ( Fig. 6e View Figure ), curving anteriorly in basal half and straight at distal half, directed up and forward at about 45° angle and inclined to the left ( Fig. 6d View Figure ). Horn looks like a half-rolled flat plate, with its anterior (dorsal) surface convex and posterior (ventral) surface concave, apex rounded. Lateral projections of posterior lobe large, pointed and separated from central horn base by deep rounded incisions. In dorsal view, prothorax posterior lobe smoothly rounded, but incision of central horn, with lateral lobes hooked inside.
Mesostigmal plate seen from above ( Fig. 6c View Figure ) composed of two yellowish, transverse, hollowed parts, long triangular with slightly convex margins and slight rounded anterior ridges at middorsal suture. Synthorax ( Figs 3b View Figure , 6a View Figure ) saturated olivaceous-green dorsally changing to saturated bluish-green at sides when alive, ochraceous to dirty bluish-greenish in the dried specimen; synthorax venter whitish without dark marking.
Legs ( Figs 3b View Figure , 6a View Figure ) yellowish-white with blackish-brown parts as follows: continuous stripes along extensor surface of femora (broader at profemora), femora apices, protibia bases, segment joints of tarsi; spines blackishbrown, claws light brown with blackish apices.
Wings as in male but larger: antenodals Px: 13 in FW, 12 in HW. Pterostigmata ( Fig. 6b View Figure ) similar in both wings, brownish-black, with a light margin, costal side twice as short as inner side, which is slightly shorter than underlying cell; both transversal sides convex, proximal one slanting, distal one perpendicular; distal half of its ventral margin thickened.
Abdomen as in male with differences at last segments ( Fig. 6f View Figure ): S8 tergite indistinctly lightened at anterioventral corner, S9 with a pair of large dorsolateral whitish spots, S10 whitish, changing pale brownish below, appendages whitish, ovipositor yellowish-white, brownish at margin.
Immature females. Immature females have crimson red thorax (including prothorax) and legs, somewhat paler ventrally, but are otherwise colored as mature ones ( Figs 2a, c View Figure , 8 View Figure ). Transitory stages to mature state not observed.
Variation in females scarce ( Fig. 2b, d View Figure ). All female paratypes from Phú Quốc have the prothoracic horn directed anteriorly, not inclined to any side. In the Phú Quốc female series, it is strongly curved, as in males, in three paratypes ( Fig. 8 View Figure ), slightly curved in one, virtually straight and raised upward more than in the Cambodian paratype in one (and is distorted in one). The lateral projections are almost absent and blunt in the immature female ( Fig. 8 View Figure ), but well developed in the five mature ones, somewhat varying in curvature. Px in HW12–14.
Measurements of females (mm). Abdomen without appendages 33–37; HW 21–23; total length 39–43.
Short diagnosis. An Amphicnemis species with a long process on prothorax posterior lobe, strongly curved anteriorly in males, straight to strongly curved and directed dorsally and anteriorly in females, a slightly arched upper male cercus branch with a small basodorsal projection directed up- and inward.
Differential diagnosis. The new species belongs to the Amphicnemis ( wallacii ) species group suggested by Dow (2014), which includes 12 species characterised by unicolorous pterostigmata, similar in all wings ( Figs 4b View Figure , 6b View Figure ). In this group, five species, including the current new species, have males with a long prothoracic horn. Of these species, A. annae Lieftinck, 1940 has this horn much longer than the prothorax median lobe; in A. triplex Dow, 2014 it is slightly longer; and in A. billitonis Lieftinck, 1940 , A wallacii Selys, 1863 and the new species it is shorter than the prothorax median lobe ( Lieftinck 1940, 1953; Dow et al. 2010; Dow 2014). In males of the new species this horn ( Fig. 4c View Figure ) is similar to that of A. wallacii and especially of A. billitonis ( Lieftinck 1940) , but is much more curved anteriorly.
While the new species is most similar to A. billitonis in the structure of its prothorax and differs from that of the hornless males of A. gracilis (see Dow et al. 2010: Fig. 8 View Figure ), its male appendages ( Figs 5 View Figure , 7e–g View Figure ) strongly resemble those in A. gracilis ( Fig. 7a–d View Figure ) ( Lieftinck 1940; Dow et al. 2010). The upper branch of the cercus is similar, but the expanded distal part is relatively longer, and in lateral view ( Fig. 7e View Figure ) better defined, with a hint of a slight ‘heel’ at its proximal part, and with a much less convex lower margin. The branch itself is more curved in lateral view, with a more concave ventral margin of its proximal part ( Fig. 7e View Figure ).
The lower cercus branch has a more defined ‘neck’ before its broadened apical part, especially in dorsal and ventral views ( Fig. 7f–g View Figure ). However, this may be an artifact of drying, especially after treatment with acetone, as the structure is quite soft and delicate. The second author made a close-up photo of the appendages of one of the Phú Quốc male paratypes when it was still fresh, and it shows ( Fig. 8b–c View Figure ) the lower branch with only a slight ‘neck’ identical to that of A. gracilis ( Fig. 7a–d View Figure ).
Male genital valves ( Fig. 4f View Figure ) in the new species are of the same shape as in A. gracilis and A. bebar ( Dow et al. 2010) , but their inner margins are nearly touching, rather than clearly separated.
A more or less long prothoracic horn is found in females of 10 of 12 species of the Amphicnemis ( wallacii ) group including the abovementioned ones and A. bebar Dow, Choong & Ng, 2010 , A. erminea Lieftinck, 1953 and A. triplex Dow, 2014 , and is absent only in A. kuiperi Lieftinck, 1937 (no horn) and A. smedleyi Laidlaw, 1926 (a very short horn) ( Lieftinck 1940, 1953; Dow et al. 2010; Dow 2014), but no female descriptions were published for A. mariae Lieftinck, 1940 and A. remiger Laidlaw, 1912 . Some populations of A. annae are polymorphic with respect to the presence of the horn, although it is absent in most of them (R. Dow, pers. comm.). In females of the new species this horn, directed up and forward ( Fig. 6c View Figure ), is also most similar to that of A. billitonis , as in males. Identification of Amphicnemis females is mostly based on the prothorax structure ( Lieftinck 1940; Dow et al. 2010) but we cannot differentiate the females of the new species from A. billitonis .
Habitat. In Cambodia, individuals of the new species were flushed from herbs on shady ground bluffs 1–2 m high at the banks of a small and shallow permanent nameless (?) rivulet with a dark bottom ( Fig. 9 View Figure ) crossing lowland evergreen forest on a coastal flatland 1.7 km from its fall to the sea. The individuals hung from leaf tips or perched on twigs over a muddy ground or at moist ground bluffs of rivulet banks. No individual of this species was found during earlier visits to the same locality on 27 v 2013 (Kosterin 2014) and 27 iii 2015 ( Kosterin 2015a); note the latter date to be in the same season as when the new species was found (4–5 iii 2017). For other Odonata species found in this locality see Kosterin (2014, 2015a).
On Phú Quốc Island of Vietnam, the species was commonly observed in August 2016 in, likely year-round wet, swamp forest. Individuals of both sexes perched on leaves and twigs on the ground, or hung from the tips of nearby leaves. Towards dusk, they moved higher up into the vegetation. Although the same habitat was surveyed in the winter, no individuals could be located.
Amphicnemis species are known to usually inhabit swampy forests ( Dow et al. 2010) and so did the new species on Phú Quốc. At the same time, although its Cambodian type locality was in a moist lowland evergreen forest, it was well drained by the rivulet. There were areas of swampy forest elsewhere in this forest, e.g. as closely as 0.6 km to the northeast, but no Amphicnemis was found there.
In Koh Kong Province of Cambodia, G. Chartier (pers. comm.) photographed an immature (red) female at thickets, which included Pandanus odorifer (Forssk.) Kunze and some mangroves, overhanging the lower reach of a small river (a tributary of the large Tatai River estuary), at sea level, with brackish water under tidal influence. This stream crossed a marshy coastal flatland transitory to mangroves, with abundant spikerush ( Eleocharis sp.) and stands of Melaleuca cajuputi Powell and a submangrove palm Licuala spinosa Roxb.
Distribution. The species is reliably known from two localities, on Ream Peninsula, which is a part of the larger Kampongsaom Peninsula, in Cambodia and from Phú Quốc Island in Vietnam. Although located in different countries and separated by sea, these localities are just 40 km apart. Two smaller Cambodian islands, Thmei and Sês, lie between Ream Peninsula and Phú Quốc Island. So, in addition to the rather short distance, these two localities are also separated by three narrow straits, 0.4, 1.4 and 4.3 km wide at their narrowest points. The species can thus be expected to also inhabit at least the two intermediate islands. The immature female with a prothoracic horn photographed in Koh Kong Province could not be positively identified, but is unlikely not to be this species. Its location was 127 km NW from the type locality, separated by the large Botum Sakor Peninsula. Hence the species may be widespread in lowland evergreen forests and even in forests transitory to mangroves in the southeastern Cardamom ecoregion.
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