The present thesis was carried out to extend our knowledge about the interspecies and intraspecies sensitivity differences of imidacloprid and flupyradifurone. By using the toxicokinetics-toxicodynamics models (TK-TD), the important role of biotransformation, the kinetic differences of chemicals and the intrinsic sensitivity differences of tested organisms were determined. This study supported the efficiency to use the TK-TD models in the risk assessment and recommended considering the different sizes and/or sex and temperature in the standard toxicity test.