LAUSR

The presented study is the first attempt to clarify the taxonomic composition of the Trechus “subnotatus” species group sensu Jeannel (1927) in Bulgaria. The study is based on the material collected during field expeditions in Bulgaria from 2009 to 2021 and collections of some European museums and institutions. As a result, based on the morphology of the male aedeagi, five taxa (species and subspecies) of the T. “subnotatus” group were confirmed in the territory of Bulgaria, one of which is a new species to science and is described here: T. asiaticus Jeannel, 1927; T. cardioderus irenis Csiki, 1912 (stat. nov.); T. cardioderus athonis Schatzmayr, 1909; T. cardioderus balcanicus Jeannel, 1927 (stat. res.), recognized as a valid subspecies in the present study and T. strandzhensis, sp. n. T. cardioderus irenis remained as a valid name since we found consistent differences between its syntype, the Bulgarian material of the species and T. cardioderus cardioderus. Previously reported T. subnotatus subnotatus Dejean, 1831 and T. cardioderus golesnicensis Apfelbeck, 1918 were not proved to be present in Bulgaria. A stepwise discriminant analysis was conducted to reveal the most significant morphometric characters for species identification. It showed grouping to some extent, although the groups overlapped and formed a gradient.