The objectives of our research were: (1) to assess the influence of the frequency of mowing different types of seminatural meadows characteristic of Central Europe on their floristic diversity, (2) to indicate the optimal management method (3) to estimate changes in species richness of phytophagous beetles from the Chrysomelidae family under the influence of mowing, against the background of different types of meadows. Studies conducted in a single Natura 2000 site (The Middle Wieprz Valley PLH060005) in eastern Poland have shown that mowing frequency affects both the flora and fauna diversity of seminatural meadows typical of Central and Eastern Europe. The greatest alpha-diversity was found in double-mow meadows, while the least was found in the unmown ones. Therefore, double-mowing of meadows could be a recommendation for agri-environment-climate programs that support environmentally friendly farming methods in the European Union. The Renyi diversity profiles made it possible to observe differences resulting from the frequency of mowing, especially in relation to single-mow meadows. Wet meadows (Molinietalia) and mixed meadows (Molinio-Arrhenatheretea) had similar characteristics, both in the case of single and double mowing, with a more uniform coverage of species. The least floristic diversity, expressed in species richness, was characteristic of rush meadows, while the largest was of fresh meadows. The greatest decline in chrysomelid beetle species richness was observed in rush and wet meadows, while an increase was observed in fresh meadows. Higher-order indices are easier to interpret when expressed in Renyi series. The assessment could also apply to ecosystems other than grasslands. Due to the differences obtained in the values of individual orders, it is more advantageous to use Renyi indices, especially when it comes to interpreting the occurrence of dominant species in the community. Only in the case of fresh meadows, a simultaneous increase in the alpha and beta-diversity coincided with a higher frequency of mowing. In the case of the other meadow types, with an increase in mowing frequency, higher diversity but lower beta-diversity was found.