Idionyx victor Hämäläinen, 1991

Zhang, Haomiao & Tong, Xiaoli, 2010, Descriptions of the final instar larvae of three Chinese Idionyx species (Odonata: Anisoptera: Corduliidae), Zootaxa 2716, pp. 53-63 : 57-62

Idionyx victor Hämäläinen, 1991

Figures 21 –29, 34–35, 38–39

Material examined. 5 final stage larvae, 01.IV.2008, The Diaoluoshan National Nature Reserve (18°43ʹ37ʺN, 109°52ʹ20ʺE), Hainan Province, China, Haomiao Zhang leg.; 1 ɗ and its exuviae, same data, emerged on 16.V.2008, 1 Ψ, 19.IV.2009, Xinglong (18°42ʹ47ʺN, 110°10ʹ56ʺE), Hainan Province, China, Haomiao Zhang leg.

Ground color of body yellowish brown with dark brown maculation ( Fig. 38 ). Small sized with body length 14.0 mm, head width maximum 4.0 mm; length of hind femur 4.5 mm.

Head—Mouthparts very similar to I. selysi ( Figs. 21–23 , 34–35 ) but differing by rounded apex of incisors and length of antennal segments as follows (mm): 0.16: 0.19: 0.31: 0.19: 0.19: 0.28: 0.28.

Thorax—Thorax almost as broad as the transverse diameter of head; pronotum strongly developed ( Fig. 24 ) with 3 transverse depressions; synthorax fringed with long setae; wing pads strongly divergent extending to basal 1/3 of S7. Legs long and slender, femora and tibiae each with more than 10 long, erect, pointed setae dorsally and ventrally; femora yellowish with two dark brown stripes submedially; tibiae yellowish with dark brown maculation basely.

Abdomen—Similar to I. selysi but with paler ground color and spots.

Distribution. China (Guangdong, Guangxi, Hainan, Fujiang, Hunan, and Hong Kong)

Remarks. The larvae of I. carinata , I. victor , and I. selysi are similar in appearance and coloration, but I. carinata can be easily distinguished from the latter two species by the anterior margin of prementum with approximately 20 setae at each side and small size lateral spines at S8 and S9, whereas both I. victor and I. selysi possess 11-13 setae at each side on anterior margin of prementum and large lateral spines on S8 and S9. Idionyx victor can be easily separated from I. selysi by the femora and tibiae each with more than 10 long, erect, pointed setae dorsally and ventrally, whereas I. selysi have only 4-5 long, prostrate, stout, clavate setae dorsally. The majority Idionyx adults have metallic green thorax and yellow stripes and are all similar in appearance, but they can be separated each other by the male caudal appendages. The shape of male caudal appendages are similar in I. selysi ( Figs. 19–20 ) and I. victor (Figs. 28–29), but I. selysi possesses a pointed horn-shaped prominence on segment 10 ( Figs.17, 19 ), lacking in I. victor (Figs. 26, 28). Their females are also similar but I. selysi possesses an incomplete antehumeral stripe ( Fig 18 ) lacking in I. victor (Fig. 27). Idionyx carinata is easily distinguished from I. selysi and I. victor by the shape of male caudal appendages ( Figs. 8–10 ) and, in the female, by presence of a horn on top of frons ( Figs. 6–7 ). The labrum of I. carinata is black ( Figs. 5–7 ), not white as in I. selysi ( Fig. 16 ) and I. victor (Fig. 25).

Biological notes. Members of the genus Idionyx appear to be montane, presumably breeding in forest streams. Adults are inactive and hang on the shady branches of riparian vegetation when sunny, but they actively forage within gloomy canopy of riparian vegetation where their preys are to be found. Males usually patrol for females along forest edges and shady paths. We observed a pair of Idionyx selysi mating in the shady tree near the forest edge at noon. Adult fight period is from April to August in China.

Idionyx larvae usually inhabit pool areas at headwater or lower order mountainstreams within shady canopies of riparian vegetation. Larvae are sit-and-wait foragers with their long legs and spidery shape, and often sprawl on fine sandy bottom, leaf litter, or roots of aquatic weeds and wait for their prey.

Figures

FIGURES 21 – 24 Larva of Idionyx victor Hämäläinen: (21) labial mask, dorsal view; (22) right palpal lobe, ventral view; (23) antenna; (24) pronotum, dorsal view.

FIGURES 36 – 41. 36 – 37. Idionyx selysi Fraser: (36) final instar larva; (37) male adult; 38 – 39. I. victor Hämäläinen: (38) final instar larva; (39) male adult; 40 – 41. I. carinata Fraser: (40) final instar larva; (41) male adult.

FIGURES 30 – 35. Inner surface of mandibles of Idionyx larvae: 30 – 31. Idionyx carinata Fraser: (30) right mandible; (31) left mandible; 32 – 33. I. selysi Fraser: (32) right mandible; (33) left mandible; 34 – 35. I. victor Hämäläinen: (34) right mandible; (35) left mandible.

FIGURES 16 – 20. Idionyx selysi Fraser: (16) head, male, frontal view; (17) thorax and abdomen, male, lateral view; (18) thorax and abdomen, female, lateral view; (19) caudal appendages, male, lateral view; (20) caudal appendages, male, dorsal view.

FIGURES 5 – 11. Idionyx carinata Fraser: (5) head, male, frontal view; (6) head, female, frontal view; (7) head, female, lateral view; (8) caudal appendages, male, dorsal view; (9) caudal appendages, male, lateral view; (10) thorax and abdomen, male, lateral view; (11) thorax and abdomen, female, lateral view.