Abstract. The species of the Poecilimon heroicus-group occur around the Caucasus (from north-eastern Turkey to south-eastern Ukraine). We describe the diagnostic morphological characters of all these species and the male calling song of three of the four species. Based on this data the following phylogenetic relationship is derived (P. tschorochensis (P. tricuspis (P. heroicus, P. bifenestratus))). Within the genus Poecilimon, the species can be recognised by a relatively wide pronotum and large tegmina. In one species, Poecilimon tschorochensis Adelung, 1907 (type species of the monotypic genus Artvinia Karabag, 1962, syn. n.; P. rammei Miram, 1938, syn. n.), the tegmina are very large and the song has unusually low spectral components. This species produced disyllabic echemes at intervals of about 10 s. In two other species of the group, P. heroicus and P. bifenestratus, the calling song of males consists of an uninterrupted dense sequence of long syllables (syllable duration around 0.5 s; ca. 1 syllable/s at 20°C). In these species the auditory spiracles are reduced in size in both sexes, and the females have extremely small tegmina and are unable to respond to the male song acoustically, which would be typical for Phaneropteridae. The change in communication from acoustically responding to mute females has not been previously documented within a group of closely related species.

ISSN (online): 1802-8829http://www.eje.cz many species diffi cult to identify. The results of recent cytogenetic and molecular genetic studies contradict morphological and bioacoustic data (Warchalowska-Sliwa et al., 2008;Grzywacz-Gibała et al., 2010). We believe that the investigation of the acoustic signals of Isophya males as taxonomic characters could not only be useful for species diagnostics but also provide additional material for a better understanding of the taxonomic position of several species and evolutionary trends in the genus Isophya. Songs of specimens of different species collected in the eastern part of the range of this genus can provide additional data for analysis of the geographical variability in sound signals. Previously data on the songs of several species were published by Zhantiev and co-authors (op. cit.). However, these results do not contain a full description of song structure, frequency spectra and stridulatory fi les. This article fi lls these gaps and provides new data about some rare species. MATERIALS AND METHODSAdults or nymphs of different instars of bush-crickets collected in natural habitats were brought to the laboratory where bioacoustic and most behavioural experiments were performed. Tape recordings of the calling song of I. doneciana were obtained only in the fi eld. We usually used 3-5 specimens for bioacoustic studies, but in the cases of some rare species only one male was available (see note in the text).Laboratory

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