Aims of this dissertation were to contribute to a better knowledge of the entomofauna of our country with special emphasis on the biology and ecology of endemic species, a combination of morphological and molecular methods to contribute to the resolution of taxonomic relationships between selected endemic species of the genus Carabus and to recognise possible changes in the composition of the carabids' assemblages in the Risnjak National Park after period of 25 years. For the first time, in this study, we used the mitochondrial sequences of two endemic species Carabus (Platycarabus) creutzeri, Carabus (Eucarabus) parreyssi and another Eucarabus species Carabus ulrichii in the reconstruction of the Carabus phylogenetic tree. Combining traditional morphometry, geometric morphometry and molecular analyses, we attempted to determine the phylogenetic relationships within two sister endemic species of the genus Carabus - C. croaticus and C. caelatus and to determine the true number of subspecies and phenotypic variants. A significantly smaller number of subspecies have been suggested, and geometric morphometric methods have also proved to be useful for intraspecific delimitation, overcoming traditional linear morphometry problems. An analysis of the carabids' assemblages after 25-years indicated a decrease in the number of mountain specialists and the spread of generalists within the Risnjak National Park. The absence of endemic species Molops alpestris, Pterostichus unctulatus and Trechus croaticus in the catch highlight the importance of further continuous monitoring of carabids' assemblages to take accurate and well-timed conservation measures.