Bayadera strigata Davies & Yang, 1996

Yang, Guo-Hui & Orr, Albert G., 2024, The final-instar larva of Bayadera strigata Davies & Yang, 1996 from Yunnan, China (Odonata: Zygoptera: Euphaeidae), International Journal of Odonatology 27, pp. 11-18 : 12-15

Bayadera strigata Davies & Yang, 1996

( Figs 1 , 2 , 3 , 4 , 5 , 6 , 7 )

Material examined Head. Broad and pentagonal in shape, flat dorsally, covered with numerous fine setae on the dorsum except on the vertex ( Figs 2 , 3a ). Labrum with long SS and scattered CVS on basal, and dense CVS and short SS at 4/5 of the base of the labrum ( Figs 3a–b ). Compound eyes broad and rounded, protruding anterolaterally. Occiput margin concave, with scattered SPS; postocular lobes strongly developed and rounded, but dense SPS at the posterior corners create a seemingly squared profile; anterior margin with CVS along the margins of the compound eyes, posterior margin intermingled with small spines, long SS and CVS. Genae large, with rows of SPS and CVS along the ventral margins of the compound eyes; anterior margin of right gena with rows of blunt and distinct spines (7–8) and a row of CVS infused with SPS and SS ( Figs 3b–c ); anterior margin of the lef gena with a row of 9–10 dominant spines and row of CVS infused with SPS and SS ( Figs 3d–e ). Antennae unusually long (1.3 × length of head measured from occipital margin to labrum), filiform, 7-segmented; third antennomere longest, length of antennomeres (mm): 0.67:0.8 6:1.23:0.83:0.46:0.23:0.09, giving a total length of 4.37 ( Fig. 4a ). Prementum 1.4 × longer than wide, subpenta- 1 ♀ larva, 6.iv.2020, ZiYang stream (25.74° N, 99.99° E, 2320 m a.s.l.), YangBi County, Bai Autonomous Prefecture of Dali , Yunnan Province, China, Guo-Hui Yang leg. The ZiYang is one of steams on Mt Cangshan in Dali, Yunnan. 2 ♀♀, 2 ♂♂ larvae, 27.iv.2023, same locality, Guo-Hui Yang leg. 1 ♂ F-0 adult emergence 2.vi.2023 ; 2 ♂♂ larvae, 27.ix.2023, Mt Maer (26.25° N, 100.13° E, 2750 m a.s.l.), HeQing County, Bai Autonomous Prefecture of Dali, Yunnan Province, China, Dong-Dong Zi leg. 1 ♂ F-0 successful emergence 4.xi.2023 .

Description

Habitus. A medium-sized larva, somewhat flattened, robust build, with long heavy legs; colour brownish black, lacking a distinct pattern, with dark saccoid gills with blunt and pale tips ( Fig. 2 ).

gonal in shape, with a row of 14–16 (lef side) and 13– 17 (right side) strong broad spines and numerous small spines (each spine bearing SS) along the lateral margin of each side ( Figs 4b–c ); ligula convex, its anterior margin finely serrated, with a tiny median clef ( Fig. 4d ); labial palp long, 0.54 × as long as the prementum, outer margin with scattered SS and CVS, while SS, CVS and SPS are dense in the basal half, weakly serrated on the inner margin, distal end with three processes, the outer process moderately incurved with a wavy outer margin, the middle process largest, weakly unciate, the inner process short and securiform, movable hook about 0.44 × as long as the labial palp, acuminate, bent slightly inwards ( Fig. 4e ). Mandibles brown, formula:

L 1+1’2340 a(m 1.2.3.4.5)b / R 1+1’234 y a(m 0)b, asymmetrical,fourincisors,welldeveloped,4>3>2>1+1’; molar crest with seven teeth (a>1=2=3=4=5>b) on lef mandible; a>b, b very small on the right mandible ( Figs 4f–i ); Maxilla with seven hooks, four long and three short, sharply pointed, basally with short setae; maxillary palp bearing dense, long setae ( Figs 4j–k ).

Thorax. Prothorax trapezoidal, narrower than the head, with scattered CVS intermixed with SS. Procoxa arc-shaped, with a central protrusion, and supracoxal armament on prothorax circularly arc-shaped, with a depression in the middle, lateral margin of pronotal disc rounded ( Figs 2 , 3a ). Synthorax nearly equal to head in width, covered with SS on its dorsal side. Wing sheaths divergent, forewing sheaths reaching the rear border of S5, hindwing sheaths extending to middle of S6. Legs long and robust; metafemur straight, reaching distal end of S7; all femorae and tibiae bearing SS and CVS; a row of claviform to rod-like setae on the distal end of the tibial comb; tarsal formula 3-3-3; claws small and simple ( Figs 2 , 5a ).

Abdomen. Long, gradually narrowing from S1 to distal end, with scattered CVS and SS; seven pairs of pale lateroventral abdominal gills from S2 to S8. Male gonapophyses well developed, base stout, tips blunt, moderately divergent distally in ventral view, reaching more than halfway along S10, with a plate-like spine on the ventral side ( Figs 5b–c ); female gonapophyses rising from the distal end of S8 and basal S9 and extending almost to the distal margin of S10 ( Figs 5d–e ); lateral valvulae each with a nipple-shaped process at the tip and a plate-like spine on the ventral side; cerci in both sexes long, narrow, slightly curved with pointed tips, bearing claviform to rod-like setae; male paraprocts triangular. Caudal gills brownish black, swollen, saccoidshaped, with a yellowish white terminal filament, covered with SS; median gill about as long as the lateral gills ( Figs 5f–h ).

Measurements (mm). Larvae (in alcohol, N = 7), body length (excluding antennae and caudal gills) 14.8–16.2; length of abdomen (including caudal gills) 14–15.4; maximum width of head 5; length of hind femur 5–6.5; lateral caudal gills 7–8.

Figures

Figure 1. Caudal appendage of Bayadera strigata, (a) dorsal view; (b) lateral view.

Figure 2. Larval habitus of Bayadera strigata, dorsal view.

Figure 3. Head of a larva of Bayadera strigata and morphological details of the labrum and genae: (a) head, dorsal view; (b) labrum, dorsal view; (c) right genae; (d) lef genae; (e) detail of arrangement of the spines and setae along the margin of the right genae; (f) detail of arrangement of the spines and setae along the margin of the lef genae.

Figure 4. Details of the head and mouthparts of the final instar of Bayadera strigata: (a) right antenna; (b) labium, ventral view; (c) labium, dorsal view; (d) ligula, dorsal view; (e) labial palp, ventral view; (f) right mandible, ventral view; (g) right mandible, inner face; (h) lef mandible, ventral view; (i) lef mandible, inner face; (j) lef maxilla; (k) right maxilla.

Figure 5. Morphological details of the tibia and S8–10 of B. strigata: (a) tibial comb and tarsi, dorsal view; (b) male gonapophyses, ventral view; (c) male gonapophyses, lateral view; (d) female gonapophyses, ventral view; (e) female gonapophyses, lateral view; (f) lateral caudal gill, lateral view; (j) median caudal gill, lateral view; (h) caudal gills, dorsal view.

Figure 6. (a) Final instar of Bayadera strigata in the laboratory; (b) male imago emerging on 02.vi.2023; (c) emergence of a male on 04.xi.2023; (d) male of B. strigata perched on branches next to a stream; (e) numerous males of B. strigata taking females in tandem to lay eggs on wood in turbulent rivers.

Figure 7. Larval habitat of Bayadera strigata.