On the fauna of bristletails of the genera <Emphasis Type="Italic">Petrobius</Emphasis> and <Emphasis Type="Italic">Trigoniophthalmus</Emphasis> (Thysanura,Machilidae) from the Caucasus

Five new species, Petrobius caucasicus sp. n., Trigoniophthalmus presimplex sp. n., T. divnogorski sp. n., T. kislovodski sp. n., and T. adigei sp. n. (Machilidae), are described from the Caucasus. A key to all the known species of the genus Trigoniophthalmus is given. Two subgenera (Trigoniophthalmus s. str., Trigoniocellus subgen. n.) in the genus Trigoniophthalmus are described. 2 + 2 retractile vesicles are present on abdominal segments II–IV in the species of Trigoniocellus subgen. n. and on II–V abdominal segments in Trigoniophthalmus s. str. Analysis of the evolution and phylogenetic relations between the species of the genus Trigoniophthalmus is performed for the first time. The formation of bristletails of the genus Trigoniophthalmus appears to occur in the Caucasian mountain province of the European area, from where they penetrated to the Central European mixed province and the Mediterranean subarea. Among the described species of the genus, T. kislovodski is distinguished by the greatest number of plesiomorphic states of morphological characters.