The derivatives of esters of carboxylic acids represented by the general formula I: ##STR1## wherein: R.sub.1 is an alkyl group having a chain or branched chain of 1 to 4 carbon atoms; andR.sub.2 is a group represented by the following general formulae II, III or IV; ##STR2## wherein: R.sub.3 is a hydrogen atom or a methyl group;X is an oxygen atom or a methylidene group;R.sub.4 is an hydrogen atom or an ethynyl group;R.sub.5 and R.sub.6 are alike or differently selected from the group consisting of hydrogen, fluorine, chlorine atoms or methyl group;R.sub.7 is a hydrogen atom or a trifluoromethyl group;R.sub.8 is selected from the group consisting of propargyl, methoxymethyl or methylthio groups; orR.sub.7 and R.sub.8 may combine with each other to form a methylenedioxy chain; and the process for manufacturing the same, and the insecticides and the insect proofing agents containing the same as an active ingredient.The compounds represented by the general formula I are useful ingredients of insecticides and insect proofing agents which have both a fast-acting property and a lethal effect, and moreover, are highly safe to mammals; and therefore, insecticides and insect proofing agents containing the above compounds have a highly practical use.