Key to Western Palaearctic Lyrothorax species based on median lobe of aedeagus

1 In left lateral view angulate margin of preputial field of the apical orifice (pft) very large, triangular; terminal lamella in lateral view oblique, with a large tooth (tltl) (Fig. 6b), in dorsal view short (WL-tl: 2.99–3.41), apical margin incised medially (Fig. 7b)..................................................................................... P. fritzei sp. n.

- In left lateral view angulate margin of preputial field of the apical orifice (pft) short (Figs 6a, c)....................... 2

2 Terminal lamella in lateral view straight or slightly bent, without a tooth along the left lateral margin (Fig. 6c), in dorsal view mostly long; but strongly variable (WL-tl: 1.89–3.06) (Figs 7c 1–3), Czech specimens from Moravia: 1.67–2.04, from Bohemia: 2.37–2.76), mostly apical margin medially incised (Fig. 7c)......................................... P. vagus sp. n.

- Terminal lamella in lateral view oblique, with a small tooth (Fig. 6a), in dorsal view medium long (WL-tl: 2.38–2.60), apical margin straight, in some specimens from Gilan rounded (Fig. 7a).................................. P. caspius (Mén.)