The subfamily Platycnemidinae (Zygoptera: Platycnemididae) in Thailand, with description of the final stadium larva of Copera chantaburii Asahina, 1984

Within the damselﬂy subfamily Platycnemidinae, eight species are currently recognized in South-East Asia. The ﬁnal stadium larvae of only three of them have been so far described. The ﬁnal stadium larva of Copera chantaburii is described and illustrated for the ﬁrst time, based on reared specimens, and new provincial records both of larvae and adults of C. chantaburii are also provided. The larva of C . chantaburii can be distinguished from known species by the following combination of characters: square or almost horizontal rectangular shape of the outer lobe of the labial palp and ﬁmbriated caudal lamellae that are stout at the base and narrow to an acute tip. The ﬁnal stadium larva of Pseudocopera ciliata is redescribed with possibly diagnostic characters, such as the shape of the distal margin of the labial palp, the ratio of the length of caudal lamellae length and body length, setae on the margin of caudal lamellae and the setae on the terminal ﬁlament of the caudal lamellae.

In the present paper, we provide detailed descriptions of the final stadium larva of C. chantaburii for the first time, and redescribe the larva P. ciliata.

Materials and methods
Last stadium larvae were found in lentic and lotic habitats such as swamp ponds, streams and rivers. The larvae were collected by a D-frame net. This net was suitable to sample the different microhabitats, including the leaf litter, tree roots and submerged vegetation. The last stadium larvae were transferred to the laboratory for rearing until emergence of the adults. The exuviae were also collected around their habitat. The adults were preserved in acetone and dried. The identification was performed based on caudal appendages, following Asahina (1993). The measurements (mm) and photographs were taken using a Nikon SMZ800 (Nikon Instruments Inc., Melville, [New York], USA) a Canon Visionary LK System (Dun, Inc., Palmyra, [Virginia], USA) and a Leica M205C (Leica Microsystems, Heerbrugg, Switzerland). Drawings were made on an iPad using the Procreate application (Savage Interactive Pty. Ltd., North Hobart, [Tasmania], Australia) and based on a representative digital photograph. Final plates were prepared using Adobe Photoshop CC 2017 (Adobe Inc., San Jose, [California], USA). The description of the formula of the larval mandibular formula, the caudal lamellae and the setae on the labium followed the terminology used in Watson (1956), MacNeill (1960 and Kumar (1973), respectively. Abdominal segments 1-10 and antennomeres 1-7 were indicated as S1-S10 and A1-A7, respectively. The specimens are deposited in the Aquatic Insects Collection (AIC) of the Zoological Museum, Kasetsart University (ZMKU), Bangkok, Thailand. Geographic distributions were plotted using SimpleMappr (Shorthouse, 2019). Kirby, 1890 Copera chantaburii Asahina, 1984 (Figures 1, 3a, c, 4a, c, e, g-j, 5a, c, e, 6a, c, e, g, 7a, b, Appendices 3, 4a, b, 6a) Copera chantaburii Asahina, 1984a: 7-9.
Head. Broad and robust in dorsal view, roughly squashed pentagon in outline; labrum with sparse setae on distal half and basal half glabrous, apical median emargination; frons and vertex irregular knotted, with three prominently ocelli; compound eyes narrow and rounded protruding to lateral side, furnished with numerous spiniform setae; occiput smooth convex shape, anterior margin with large protuberance at corner of compound eyes (Figure 3a, c); postocular lobes well developed, smoothed on anterior margin, with numerous spiniform setae on posterior margin; genae (Figure 4c) with row of 10 blunted stout spines and simple setae on anterolateral margin, with middle larger than other ones in left gena, with row of six blunted stout spines, larger than other ones in right gena; antennae (Figure 4a) filiform, 7-segmented, with A2 and A3 the longest, with an apical spine on A6, relative length of antennomeres 0.85: 1 (0.64 mm): 0.99: 0.78: 0.51: 0.42: 0.24; prementum (Figure 5a) subpentagonal shape extending posteriorly up to the middle of the fore coxae, with two pair premental setae, with a row of 19-23 spiniform setae along lateral margin of each side, laterodistal margin with 3 minute and 3 distinct spiniform setae and with two long setae on middle of ventral side ( Figure 5c); ligula strongly produced to form an obtuse angle, the two slightly convex sides forming an angle of about 130°, with one pair protuberances and 48 minute spiniform setae along margin; labial palp (Figure 5e) as long as 0.34 × of prementum, with 4 + 4 palpal setae, outer margin with serrate spiniform setae, distal margin divided into 2 lobes, the outer lobe forming square, truncate, denticulate lobe with 4 distinct teeth, inner lobe forming end hook blunt pointed, and movable hook slender about 0.79 × as long as labial palp, acuminate, bent inwards; maxilla (Figure 4e) galeolacinia with 6 teeth, four dorsal teeth of approximately the same size, apical teeth largest, two ventral teeth of small size. Mandible (Figure 4g-j) with well-developed long teeth on each incisor lobe, without molar crest; left mandible with five incisor teeth, two molar teeth (a > b); right mandible with five incisor teeth, one molar tooth, an additional tooth and following mandibular formula: L 1 + 1'234 a b/ R 1 + 1'234 y a.
Thorax. Narrower than head, with scattered setae, with almost hexagonal shape, anterior margin reaches to concave of postocular lobe, posterior margin forming rounded slightly keeled; prothoracic process blunted, smooth; angulated pronotum disc; synthorax with scattered setae and minute protuberance; wing pads pale with glabrous, parallel, anterior and posterior wing pads reaching to distal margin of abdominal segment 4; legs almost flat and long; femora thin with dark band on posterior side, row of spiniform setae and scattered setae; hind femora as long as 1.57 × and 1.35 × length of fore and mid femora, respectively; tibiae combed, with scattered setae and a few tridentate setae; tarsi formula: 3-3-3; two claws simple with pulvilliform empodium.
Abdomen. Cylindrical shape, slender, narrowing caudally, with scattered setae; abdominal terga with two longitudinal pale black stripes on midline, with a couple of black spots on middle between mid-line; abdominal sterna with a pale network of tracheoles, with dark spots on posterolateral side; abdominal pleura with row of setae, abdominal pleura S1-S7 flattened, with dark triangular spot, abdominal pleura S8-S10 with distinct spiniform setae on posterolateral end, abdominal S10 with cluster of spiniform setae externally at the basal of cerci; male forming the duplex gills, anterior region with yellowish smudged marking forming acutangular shape, posterior region scattered pale white spots, widely on its distal end of median trachea, strongly stout, short fimbriated on margin, median gill shorter than lateral gills; tracheation well developed, a median trachea largest, indistinct, reaching 4/5 of caudal lamellae; secondary branches, irregularly branched, little undulate extended to distal margin and small tertiary branches arise to margin side; median gill anterior portion with 5 spiniform setae on dorsal margin and sparsely 9 spiniform setae on ventral margin, median trachea with 4 spiniform setae scattered; lateral gills anterior portion with 18 spiniform setae on dorsal margin and sparsely 9 spiniform setae on ventral margin, median trachea with 7 spiniform setae array on outer side and scattered.
Description of female larva. As male, unless otherwise stated: female gonapophyses (Figure 6e, g) comprising two pairs of long valvae; lateral valvae with sharply pointed processes, slightly divergent, with a row of setae and distinct single spiniform setae on each side, reaching over sternite 10; central valvae shorter than as lateral valvae, slender, apically rounded.
Larval morphological variation. Coloration varied, yellowish cream to brownish black. Articulation of labium extended at level of middle coxae of foreleg up to anterior coxae of midleg. Genae with 7-11 rows of blunted stout spines. Prementum with row of 15-22 spiniform setae along distal half of lateral margins, laterodistal margin with 2-4 spiniform setae. Some specimens without apical spine on A6. Distal part of incisor teeth showed a consistent shape among all examined specimens. Anterior and posterior wing pads reaching half of S3 to almost S5. Caudal lamellae with irregular fimbriated margin and tip of each fimbriated forming pointed or blunted; antenodal region of median gill with 11-15 spiniform setae on dorsal margin and sparsely 2-6 spiniform setae on ventral margin, median trachea with 3-6 spiniform setae array on both sides. Antenodal region of lateral gills with 6-9 spiniform setae on dorsal margin and 9-18 spiniform setae on ventral margin, median trachea with 6-11 spiniform setae array on outer sides.
Diagnosis. The larva of Copera chantaburii is closely similar to those of C. marginipes, but it can be distinguished by (1) almost horizontal rectangular shape of outer lobe of labial palp and (2) fimbriated caudal lamellae, stout basally and narrowing to acute tip (Appendix 4a, b).

Distribution. Southeast Asia
Redescription of male larva. Larvae slender, body very long (Figure 2).
Head. Broad and robust in dorsal view, roughly squashed pentagon in outline, with scattered setae and white spot; labrum with sparse setae on distal half and basal half glabrous, apical median emargination; frons and vertex irregular knotted, with three prominent ocelli; compound eyes narrow and rounded protruding lateral side; occiput smooth convex shape, anterior margin ) subpentagonal shape extending posteriorly up to the middle of the fore coxae, with dark band on middle part, having two pairs of premental setae, laterodistal margin and 3 distinct spiniform setae, with a row of 16-18 spiniform setae along distal half of lateral margin; ligula strongly produced to form an obtuse angle, the two slightly convex sides; with one pair protuberances and a minute spiniform setae along margin; without setae on middle of ventral side (Figure 5d); labial palp ( Figure 5f) as long as 1/2 of prementum with 3 + 3 palpal setae, outer margin with serrate spiniform setae, distal margin divided into 2 lobes, the outer lobe square, truncate, denticulate with 5 distinct teeth and inner lobe bears end hook with blunt tip; movable hook slender and about 0.71 times as long as labial palp, acuminate, bent inwards; maxilla (Figure 4f) galeolacinia with 6 teeth, four dorsal teeth approximately of the same size, apical teeth largest, two ventral teeth of small size. Mandible (Figure 4k-n) with well-developed long teeth on each incisor lobe, without molar crest; left mandible with five incisor teeth, two molar teeth (a = b); right mandible with five incisor teeth, one molar tooth, an additional tooth and following mandibular formula: L 1 + 1'234 a b/ R 1 + 1'234 y a. Thorax. Narrower than head, with scattered setae and white spot, with almost hexagonal shape, scattered setae and minute protuberance, anterior margin reach to concave of postocular lobe, middle lobe with pale yellow line on mid line; prothoracic process blunted, angulated; pronotum disc smooth, rounded, slightly keeled; synthorax scattered setae and minute protuberance; wing pads pale with glabrous, parallel, anterior and posterior wing pads reaching to distal margin of abdominal segment 4; legs almost flat and long; femora thin with dark band on posterior side, row of spiniform setae and scattered unidentate setae; hind femora as long as 1.83 × and 1.34 × length of fore and mid femora, respectively; tibia comb with scattered setae and a few tridentate setae; tarsi formula: 3-3-3; two claws simple with pulvilliform empodium.
Abdomen. Cylindrical shape, slender, narrowing caudally, scattered setae, minute protuberance and white spot; abdominal terga with longitudinal pale black line, posterior margin with a couple of pale black spots on middle; abdominal sterna with a pale network of tracheoles, with scattered setae, with pale dark spots on posterolateral side; abdominal pleura flatted on S1-S9 and distinct spiniform setae on posterolateral end of S9-S10, S10 with cluster of spiniform setae externally at the basal of cerci; male gonapophyses (Figure 6b, d) sharply pointed, widely divergent in ventral view, reaching anterior margin of sternite 10, with a row of setae on ventral margin; gonopore very small, O-shape embossed and fissure on middle to posterior ( Figure 6d); caudal lamellae ( Figure 7c, d) forming simplex-denodated gills large, long and broad, with irregular light and shade markings, several irregular tiny and long setae along margin, with long terminal filament on apex of lamellae and its one pair of setae, with a little protuberance. Tracheation unclearly developed, a distinct median trachea, reaching terminal filament; secondary branches, irregularly branched, little undulate extended to distal margin and small tertiary branches arise to margin side; median lamella with length longer than 2.09 × its widest width, with 26 and 21 setae on dorsal and ventral margin, respectively, lateral lamellae with length longer than 2.47 × its widest width, with 39 and 32 setae on dorsal and ventral margin, respectively.
Redescription of female larva. As male, unless otherwise stated: female gonapophyses ( Figure  6f, h) comprising two pairs of long valvae; lateral valvae with sharply pointed processes, slightly divergent, with a row of setae and distinct one spiniform setae and followed by 7-8 small spiniform setae on each side, extending over sternite 10; central valvae slightly shorter with lateral valvae, slender, apically rounded.
Larval morphological variation. Coloration varied, yellowish cream to yellowish black. Articulation of prementum and postmentum extended at level of middle coxae of foreleg up to anterior coxae of midleg. Genae with 3-5 rows of blunted stout spine. Prementum with row of 16-20 spiniform setae along distal half of lateral margins, laterodistal margin with 2-3 spiniform setae. Mandibles show a consistent shape among all examined specimens. Anterior and posterior wing pads reaching half of S3 to almost posterior of S4. Caudal lamellae with irregular marking and numerous of setae on margin.
Diagnosis. The larvae of Pseudocopera ciliata can be distinguished from other species by setae on terminal filament on caudal lamellae and length of caudal lamellae approximately 0.95 × body length, square or vertical rectangular shape of labial palp, a few row of setae on the margin of caudal lamellae.

Measurements. See in Appendix 2
Biological notes. The larvae of Pseudocopera ciliata inhabit lentic and lotic water, such as slow flowing streams, lakes and seasonal ponds. They inhabit among submerged vegetation and leaf litter (Appendix 5b, c). They display agonistic behaviour as a tendency to keep the distal margin end of the abdomen somewhat upturned, while the caudal lamellae remain gently free and pointing headward (Appendix 6d). (Rambur, 1842) (Appendix 4c, d, 6b)

Distribution. Oriental region
Diagnosis. The larva of Copera marginipes is closely similar to those of C. vittata and C. chantaburii but it can be distinguished by (1) vertical rectangular shape of outer lobe of labial palp and (2) fimbriated caudal lamellae that are almost stout basally and narrowing to slender at middle to acute tip (Appendix 4c, d).

Distribution. Oriental region
Diagnosis. The larva of Copera vittata is closely similar to those of C. marginipes, but it can be distinguished by (1) vertical rectangular shape of outer lobe of labial palp and (2) fimbriated caudal lamellae slender from base to acute tip (Appendix 4e, f).

Discussion
Taxonomic larval characters for distinguished subfamily levels of the Platycnemididae are still uncertain because the members have highly consistent characters (Orr & Dow, 2015). However, the subfamily Platycnemidinae has synapomorphic characters, such as the protuberance at the corner of the compound eyes ( Figure 3) and two pairs of premental setae (Figure 5a, b) (Deacon & Samways, 2016;Lieftinck,1940;Matsuki, 1993). The general morphology of the genus Copera clearly differs from that of the genus Pseudocopera by the shape of the caudal lamellae (Orr & Dow, 2015) as the adult can be distinguished by genital ligula (Dijkstra, 2013). Pseudocopera ciliata is greatly similar to P. annulata and P. tokyoensis (Chowdhury & Miah, 1990;Yum & Bae, 2007). Matsuki (1993) provided distinguishing characters for P. ciliata and P. annulata, which are the ratio of the length and widest width of the caudal lamellae, and the ratio of the terminal tip and widest width of the caudal lamellae. But these characters seem to be unreliable, because ratios of these characters are highly variable among individuals of our P. ciliata specimens within the range of P. annulata. However, the present study identified possibly distinguishing characters for P. ciliata, such as the shape of the distal margin of the labial palp (square or vertical rectangular shape in P. ciliata; vertical rectangular shape in P. tokyoensis; not mentioned in P. annulata), the ratio of the length of caudal lamellae and body length (caudal lamellae length is shorter than 0.8 × body length in P. annulata and P. tokyoensis; caudal lamellae length is longer than 0.8 × body length in P. ciliata), setae on the margin of caudal lamellae (few in P. annulata and P. ciliata; numerous in P. tokyoensis) and the setae on the terminal filament of the caudal lamellae (one pair setae in P. ciliata; absent in P. annulata and P. tokyoensis) (Chowdhury & Miah, 1990;Yum & Bae, 2007). Among the five Asian species of Copera, two species (C. imbricata and C. rubripes) are poorly known so far, and no description of the larval stage is available (Lieftinck, 1940;Navás, 1934). The current analysis of the morphological characters of three known larvae allows us to summarize the taxonomic characters (Table 1) as follows: the shape of fimbriated caudal lamellae (slender basally in C. vittata; stout basally in C. chantaburii and C. marginipes) and the shape of distal margin of the labial palp (forming square or vertical rectangular shape in C. marginipes and C. vittata; forming horizontal rectangular shape in C. chantaburii). The larvae of the Platycnemidinae flourish in a wide variety of biotopes. Basically, the larvae of C. marginipes and C. vittata were usually found amidst aquatic vegetation in streams, especially headwater streams (Kumar, 1973;Saetung & Boonsoong, 2016), whereas the larvae of C. chantaburii favour lentic waters, as does P. ciliata (Chowdhury & Miah, 1990;Saetung & Boonsoong, 2019). Both Copera and Pseudocopera have dominant agonistic behaviour as the same display position in each species, which is the characteristic behaviour of platycnemid larva, (Rowe, 1992) (Appendix 6).
Copera chantaburii is only known from Thailand and Vietnam (Phan, 2019). In Thailand, Hämäläinen & Pinratana (1999), Day et al. (2012) and Phan (2019) recorded it in Chanthaburi, Lampang, Nakhon Nayok and Khon Kean provinces. Recently, further specimens and reliable photographic records have been collected, bringing the number of provinces up to 13 around the upper part of Thailand (Figure 8). Unlike the widespread C. marginipes and C. vittata, an intensive survey of Copera chantaburii is needed in the area between Thailand and Vietnam to fill in the gaps of its distribution, and another region such as Myanmar and southern Thailand.