Pyrazoline derivatives useful as insecticides having the formula ##STR1## wherein R.sup.1 represents hydrogen atom, a lower alkyl group, (CH.sub.2).sub.n CN group, (CH.sub.2).sub.n OR group, phenyl group or a halogen-substituted phenyl group; R.sup.2 represents hydrogen atom or methyl group; Y represents hydrogen atom or chlorine atom; X represents oxygen atom, sulfur atom, sulfinyl or sulfonyl group; R.sup.3 represents a halogen-substituted lower alkyl group; and n is integer 1 to 3 and R represents a lower alkyl group.