A compound of the formula, ##STR17## wherein W represents CH or nitrogen, and (1) when W is CH, R.sub.1 represents hydrogen, fluorine, chlorine, bromine or methyl, R.sub.2 represents hydrogen or fluorine, R.sub.3 and R.sub.4 are same or different and represent hydrogen, halogen, C.sub.1-4 alkyl, a C.sub.1-4 alkoxy, difluoromethoxy or 2,2,2-trifluoroethoxy, or represent, taken together, methylenedioxy, A represents oxygen, and X and Y represent, taken together, ethylene or 1,1-difluoroethylene which form a cyclopropyl ring or a 1,1-difluorocyclopropyl ring with a carbon to which they are attached, and
- (2) when W is nitrogen, both R.sub.1 and R.sub.2 represent hydrogen, and R.sub.3, R.sub.4, A, X and Y are as defined above.