Gynacantha rosenbergi, Kaup in Brauer, 1867

Theischinger, Gunther, Marinov, Milen, Bybee, Seth, Jensen, Colin, Theuerkauf, Jörn & Rashni, Bindiya, 2020, The genus Gynacantha Rambur, 1842 in the South Pacific (Odonata: Anisoptera: Aeshnidae), Zootaxa 4778 (1), pp. 171-195 : 194

Key to the species of the Gynacantha rosenbergi group (males only)

1 Minimum width at the constriction (waist) of S3 slightly less than, to slightly greater than, maximum width of S10, ratio 0.85–1.15 ( Fig. 36 a–d); superior anal appendages long compared with the width of S10, ratio 3.74–4.10, inferior appendage basally not wider than ½ width of S10 ( Fig. 36b, d ).................................... G. rosenbergi group s. str 2

- Minimum width at the constriction (waist) of S3 markedly less than maximum width of S10, ratio 0.59–0.72 ( Fig. 36e, f ); superior anal appendages shorter compared to the width of S10, ratio 3.07–3.55, inferior appendage basally wider than ½ width of S10 ( Fig. 36f )............................................................... G. rosenbergi Pacific group 4

2(1) 3 rows of cells between anal triangle and anal loop ( Fig. 36 g ); posterior section of S3 extremely expanded ( Fig. 36h )................................................................................................ G. amphora

- Only 2 rows of cells between anal triangle and anal loop ( Fig. 36 i ); posterior section of S3 extremely expanded ( Fig. 36j ).. ................................................................................................... 3

3(2) Denticles (3–10) along genital fossa restricted to posterior region ( Fig. 36a ); apex of slightly double-curved superior anal appendages curving into short, not very acute point ( Fig. 36b ).......................................... G. rosenbergi

- Denticles (8–30) along genital fossa often extending beyond posterior region ( Fig. 36c ); apex of almost straight superior anal appendages curving into acute point ( Fig. 36d )...................................................... G. dobsoni

4(1) No dark T-mark on postfrons ( Fig. 36k ); apex of inwardly sinuous superior anal appendages not pointed ( Fig. 36f ).................................................................................................. G. apiaensis

- A dark T-mark on postfrons ( Fig. 36l ); apex of straight or in-curved (converging) superior anal appendages variably pointed ( Fig. 36 q–t).......................................................................................... 5

5(4) Denticles (10–12) along genital fossa restricted to posterior region ( Fig. 36 m ) and rather densely set in a subtriangular arrangement; apex of straight superior anal appendages widely curved into a moderately long point; inferior appendage at least 1/3 length of superiors ( Fig. 36q )................................................................... G. vanuatua

- Denticles along genital fossa not completely restricted to posterior region ( Fig. 36 n–p); apex of superior anal appendages more narrowly curved into a short point, inferior appendage less than 1/3 length of superiors ( Fig. 36 r–t).................... 6

6(5) 4–5 denticles along posterior portion of genital fossa much larger than the others and thus appearing densely set ( Fig. 36o ); superior anal appendages subapically approximately twice as wide as at base ( Fig. 36s )...................... G. koroana

- Not more than 2–3 denticles along posterior portion of genital fossa markedly larger than the others ( Fig. 36n, p ); superior anal appendages subapically approximately 1½ times as wide as at base ( Fig. 36r, t ).................................... 7

7(6) Superior anal appendages almost straight ( Fig. 36r )................................................... G. vitiana

- Superior anal appendages widely in-curved (converging) ( Fig. 36t ).................................... G. stevensoni

Figures

FIGURE 36. Key structures of males of Gynacantha species. (a, c, e) S2 and S3, ventral, (b, d, f) anal appendages, dorsal: (a, b) G. rosenbergi; (c, d) G. dobsoni; (e, f) G. apiaensis; (g, i) part of hindwing, (h, j) S2 and S3, dorsal: (g, h) G. amphora; (i, j) G. dobsoni; (k, l) head: (k) G. apiaensis; (l) G. cf. stevensoni; (m–p) genital fossa, (q–t) anal appendages: (m, q) G. vanuatua; (n, r) G. vitiana; (o, s) G. koroana; (p, t) G. sp. cf. stevensoni.