6 or 10 carbon atoms or arylalkyl group having 6 or 10 carbon atoms in the aryl moiety and 1 to 4 carbon atoms in the alkyl moiety each of which is unsubstituted or substituted by carboxyl nitro cyano halogen c 1 c 4 alkyl c 1 c 4 halogenoalkyl c 1 c 4 alkoxy c 1 c 4 halogenoalkoxy or c 1 c 4 alkoxy carbonyl r 1 represents methyl ethyl n or i propyl n i s or t butyl each of which is unsubstituted or substituted by cyano fluorine chlorine or bromine methoxy or ethoxy represents propenyl butenyl propinyl or butinyl each of which is unsubstituted or substituted by cyano fluorine chlorine or bromine represents cyclopropyl cyclobutyl or cyclopropylmethyl each of which is unsubstituted or substituted by fluorine chlorine bromine methyl or ethyl represents phenyl or benzyl each of which is unsubstituted or substituted by cyano fluorine chlorine bromine methyl ethyl trifluoromethyl methoxy ethoxy difluoromethoxy trifluoromethoxy methoxycarbonyl or ethoxycarbonyl r 2 represents alkyl alkenyl or alkynyl each of which has up to 6 carbon atoms and each of which is unsubstituted or substituted by cyano halogen or c 1 c 4 alkoxy represents cycloalkyl having 3 to 6 carbon atoms or cycloalkylalkyl having 3 to 6 carbon atoms in the cycloalkyl moiety and 1 to 4 carbon atoms.