(S)-2-methyl-4-oxo-3-(2-propynyl)-cyclopent-2-enyl (1R)-trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate represented by the formula: ##STR1## is a compound excellent in controlling effect on insect pests and harmlessness to mammals.

(S)-2-methyl-4-oxo-3-(2-propynyl)-cyclopent-2-enyl (1R)-trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate rappresentato dalla formula: ## del ## STR1 è un residuo eccellente nell'effetto di controllo sui parassiti dell'insetto ed in harmlessness ai mammiferi.