Paracercion ambiguum Kompier & Yu

Ning, Xin, Kompier, Tom, Yu, Xin & Bu, Wenjun, 2016, Paracercion ambiguum sp. nov. from Lang Son, Vietnam (Zygoptera: Coenagrionidae), Zootaxa 4144 (2), pp. 263-275 : 268-273

Paracercion ambiguum Kompier & Yu sp. nov.

Material. Holotype: male (GenBank accession number: KX263718 ), Vietnam, Lang Son, Huu Lien Nature Reserve, 1-XII-2013, Tom Kompier leg . Paratypes: 1 male (GenBank accession number: KX263719 ), same information but 23-XI-2013; 1 female, Vietnam, Lang Son, Huu Lien Nature Reserve , 7-XII-2013, Tom Kompier leg . Holotype and paratypes will be deposited in Institute of Entomology, Life Sciences College of Nankai University , Tianjin, China.

Etymology. The Latin word ambiguum means puzzling or doubtful, which emphasizes the difficulty on deciding the taxonomic position of the new species.

Description. Holotype. Labium cream-white. Bases of mandibles and labrum light blue, labrum with black dorsolateral corners and central black spot on upper margin. Anteclypeus light blue, postclypeus black with light blue anterior edge and two elongated light-blue spots on posterior edge. Antefrons light blue with black anterior edge, postfrons light blue with large central black spot, narrowly connected with black to cranium. Antennal base and scape light blue, remainder of antenna black. Top of head black with two light-blue lines extending from postclypeus onto it near base of antennae. Postocular spots large, triangular, blue color. No occipital bar. Compound eyes blackish dorsally, greenish blue anteriorly and pale blue ventrally in life ( Fig. 8 ).

Prothorax black with light-blue lateral edges. Anterior lobe largely light blue, lateral lobes light-blue with interior edge black, posterior lobe black with light-blue posterior edge. Mesostigmal lamina black with light-blue lateral edges. Synthorax black dorsally with broad light-blue antehumeral stripe. Laterally blue with black markings as follows: broad black stripe over humeral suture; distinct black stripe over first lateral suture from posterior end extending almost to midpoint, arrow-shaped and broadest at anterior end; thin black line over second lateral suture that expands into half-oval at posterior end forming black spot. Legs cream-white, with blackish extensor surfaces of femora and blackish spines. Wings hyaline, with 10–11 postnodals and brown pterostigma covering one cell in length ( Fig. 9 ).

Abdomen S1 light-blue with black dorsum, black narrowest just before posterior end; S2–4 black dorsally and blue laterally, end of S3–4 almost wholly black; S5–7 black and S8–9 blue; S10 blue with basal and distal margins black dorsally; intersegment rings covered with small black spines. Caudal appendages black. Cerci a little longer than S10 and three times length of paraprocts, apically dilated and with large basal tooth. Paraproct slanting upwards at 45 degree angle, simple in lateral view ( Figs. 2–4 ). Head of genital ligula shield-like, one pair of apical lobes broad and long ( Figs. 6–7 ).

Variation in paratype. The paratype male is extremely similar to the holotype male. However, the wings have 11–12 postnodals and S10 is decorated with an I-shaped black mark dorsally.

Female. Facial pattern identical to male, but postocular spots somewhat smaller and light-blue paler and somewhat greenish. Eyes brown dorsally and green ventrally. Prothorax similar in pattern to male, but central lobe with two pale longitudinal lines along center and color of light parts of central lobe, lateral lobes and posterior lobe mixture of pale reddish brown and greenish blue, posterior lobe without horns, its hind ridge bow-shaped, straight centrally, then slightly curving forward and towards the lateral sides slightly curving caudad again. Anterior lobe largely light blue as in male. Synthorax with basic pattern as male, but light-blue more greenish, especially towards dorsum. Dorsum more brownish and with thin paler lines along dorsal carina. Black antehumeral stripe with two pale brown lines nested in, one on either side of humeral suture, as in several other Paracercion species. Arrowshaped line along first lateral suture distinct as in male, but thin line over second lateral suture absent. Only halfoval spot towards posterior end of second lateral suture present. Legs and wings as male ( Fig. 10 ). The abdomen is thicker than that of the male, giving a more robust appearance. Abdominal segments S1–7 pale blue laterally, progressively less distinct towards S7, and blackish along dorsum. Black widest at posterior end of segment along intersegmental ring, forming incomplete rings, and blue extending towards dorsum at anterior end of segment along intersegmental ring. S8 almost entirely black, but with clear blue lateral markings, especially towards posterior edge. S9 blue with small black markings on dorsum at anterior end, S10 all blue. Cerci whitish, two-thirds the length of S10 and slanting downwards, simple conical. Paraproct whitish. Ovipositor reaching just past middle of S10, cream-white ( Fig. 11 ).

Measurements (mm): male abdomen + appendages 30.5; hind wing 19.0. Female abdomen 33.0; hind wing 21.5

Diagnosis. P. ambiguum can be separated from Pseudagrion species within whose range it occurs by characteristics of patterning (for instance, in the male a black line on the first lateral suture and in females the double lines bordering the humeral suture). The female also lacks the horns on the pronotum that are characteristic of Pseudagrion females. The long cerci of the male separate it from all other Paracercion species, but not from P.

dorothea and P. plagiosum , which also have cerci at least as long as S10. However, P. ambiguum differs from both in lateral view by having the ventral tooth at the base of the cerci where the base is so large that it extends twothirds of the length of the appendage. The tooth is only half as long as it is wide. In P. dorothea the basal tooth is long and slender and in P. plagiosum it is similarly longer than wide. In P. plagiosum the apex of the cerci is tapering and in P. dorothea it appears bifid, butin P. ambiguum the apex is robust and rounded. The paraproct is robust and upward slanting in P. ambiguum , close and parallel in lateral view to the basal spine of the cerci and extending to about one third of the length of the cerci. In P. do ro t h e a the paraproct is short, triangular and carries two spines. In P. plagiosum the paraproct has a short, curved spine, not nearly as robust as in P. ambiguum , and not following the line of the basal tooth of the cerci closely. In addition, the body of P. ambiguum is obviously slimmer than P. dorothea as well as all other Paracercion species examined. The female can be identified by the hind ridge of the pronotum, which differs from those of both P. dorothea and P. plagiosum by its bow-shaped outline, straight in the middle, then curving first forward then backward again towards its lateral ends. In P. do ro t h e a there are foliate outgrowths on either side of the hind ridge and in P. plagiosum the hind ridge is undulating, but lacks the straight middle. This straight middle section is at least lacking too in P. calamorum , P. barbatum , P. v-nigrum , P. melanotum , P. sieboldii and P. hieroglyphicum .

Notes on habitat and behavior. Unlike most Paracercion species, P. ambiguum behaves much like the Pseudagrion species it occurs side-by-side with at the type locality. Males typically hang from tips of vegetation, between just a few cm and 30 cm, over the water surface along the edge of a slow streaming river, about 10m wide, or along the edges of the reservoir from which the stream originates. Males are easily found, even under less promising cloudy conditions, but females are rarely observed and only visit to oviposit, presumably foraging at some distance from the water. Males were observed to interact with Pseudagrion spencei and P. microcephalum for positions on leaves. Other coenagrionid species common along the same stream include Paracercion calamorum and Pseudagrion rubriceps , with Paracercion melanotum scarcer. P. ambiguum has not been seen to interact with these other Paracercion species, which display rather different behaviour, perching on floating weeds rather than hanging from vegetation along the water’s edge. Observations have been made with earliest date March 22 and latest December 7, but the species may well occur year round. It is relatively common, with at least 10 males observed during each visit.

Figures

FIGURE 2. Male caudal appendages of Paracercion ambiguum, dorsal view.

FIGURE 3. Male caudal appendages of Paracercion ambiguum, lateral view.

FIGURE 4. Inner view of the right cercus and paraproct of Paracercion ambiguum, with left cercus and paraproct removed.

FIGURE 6. Male genital ligula of Paracercion ambiguum, ventral view.

FIGURE 7. Male genital ligula of Paracercion ambiguum, lateral view.

FIGURE 8. Face of male Paracercion ambiguum.

FIGURE 9. Field photo of male Paracercion ambiguum.

FIGURE 10. Head and thorax of female Paracercion ambiguum in life.

FIGURE 11. Field photo of female Paracercion ambiguum.