Key to adults of Zwicknia from western Switzerland

1 Macropterous (Figs. 4, 9 and 14). Cubital cell of forewing delimitated by the two cross-veins between veins Cu1 and Cu2 quadrangular in shape (Figs. 4, 9 and 14; Aubert 1959: 26, Fig. 22; Murányi et al. 2014: 31, Fig. 56). Posterior margin of subgenital plate (sternite 8) rectilinear or slightly rounded (Fig. 5)........... adult females of Zwicknia (not keyed out further)

- Micropterous (Figs. 1 and 6) or brachypterous (Figs. 10 and 13). Presence of an epiproct sclerite bent over the last tergites; tergite 9 with a characteristic process (Figs. 3, 8 and 12). Presence of a ventral vesicle at the center of the posterior margin of sternite 9 (Figs. 2, 7 and 11)......................................................... 2 (adult males of Zwicknia)

2 Brachypterous (Figs. 10 and 13). Tip of main epiproct sclerite long, slender, regularly bent and pointed at apex, in lateral view (Fig. 12). Process on tergite 9 high, perpendicularly raised and less than twice as wide as the main epiproct sclerite (Fig. 12; Boumans & Murányi 2014: 8, Fig. 2). Ventral vesicle half as wide as the subgenital plate (Fig. 11)..... Zwicknia westermanni

- Micropterous (Figs. 1 and 6)............................................................................. 3

3 In lateral view, the tip of the main epiproct sclerite is ogive, neither up-curved nor down-curved (Fig. 3). In dorsal view, the main epiproct sclerite is long and slender, with nearly parallel edges and without bulges (Reding et al. 2016: 140, Fig. 4). Process of tergite 9 low, rising sharply near the distal region of the corresponding tergite, not projecting caudally (Fig. 3). Ventral vesicle small, rounded at apex; width about ¼ to 1/5 of the subgenital plate (Fig. 2; Reding et al. 2016: 141, Fig. 5)............................................................................................... Zwicknia ledoarei

- In lateral view, the tip of the main epiproct sclerite is pointed, slightly up-curved (Fig. 8). Process of tergite 9 high and perpendicularly elevated, in lateral view (Fig. 8), arch-shaped in dorso-caudal view (Murányi et al. 2014: 58, Fig. 120). Ventral vesicle covering slightly less than half the width of the subgenital plate (Fig. 7)........................... Zwicknia bifrons