Key to Caucasian Perla species based on male penial setae patterns

1 Sac of the penis dorsomedial bears a tongue-shaped lobe covered with a relatively wide apical brush; the spines of the brush along the lateral edges of the sac are absent (Figs. 77−79, 108−111)..............................................2

− Sac bears a narrow apical brush (Figs. 9−10).................................................................3

2 Tube of the penis with constriction in the distal 1/3 before the sac; the sac is large, 1/3 wider than the tube, and covered with a loose triangular apical brush (Figs. 108−111). North Caucasus. Russia, Krasnodar Kray. Armenia, Georgia, Azerbaijan, and Turkey. Up to 2000 m. Adult presence: May–August............................... P. pallida Guérin-Méneville, 1843

− Tube of the penis without constriction; the sac width is the same as the tube width; ventrally, the sac is deeply depressed (Figs. 77−79). Russia, Krasnodar Kray the Black Sea coast of the Caucasus from Tuapse to Sochi. Up to 200 m. Adult presence: July............................................................................ Perla schapsugica sp. nov .

3 Sac is membranous, without tiny setae (Figs. 34−35)......................................................... 4

− Sac is membranous and covered with tiny setae (Figs. 139−140, B, D).............................................5

4 Sac bears a narrow apical brush; additional ventral brush is absent (Figs. 33−35). Caucasus. Russia, North Ossetia-Alania. Iran, Alborz Mountains. 1770−1900 m. Adult presence: June−July.................................. Р. persica Zwick, 1975

− Sac bears a narrow apical brush and an additional small ventral brush (Figs. 10, C). North Caucasus. Russia: Adygea, KarachayCherkessia, North Ossetia-Alania, Krasnodar Kray. Abkhazia. Georgia. Adult presence: late May–August...................................................................................... P. caucasica Guérin-Méneville, 1843

5 Sac covered with tufts of tiny setae associated with patches and arranged in concentric lines, following the shape of the lobes (Figs. 139−140, B, D). North Caucasus. Russia, Krasnodar Kray. Up to 1800 m. Adult presence: June.................................................................................................... Perla palatovi sp. nov .

− Sac covered with dense, tiny setae spaced relatively evenly (Figs. 58, D). Armenia, Azerbaijan. 1400–1850 m. Adult presence: latter half of May−first half of July............................................... P. kiritshenkoi Zhiltzova, 1961