Organophosphorus compounds and its insecticides acaricides and nematocides containing same

Insecticidal, acaricidal or nematocidal compositions which comprise organophosphorus compounds of the formula (* CHEMICAL STRUCTURE *) wherein R1 and R2 each represents a C1 to C4 alkyl group; X represents NH or N-R4 wherein R4 represents an alkyl; an alkenyl; an alkynyl; a phosphoric acid ester radical; a cyano group; a group of formula (II): (* CHEMICAL STRUCTURE *) (II) (wherein R5 represents an alkyl or alkylamino group); or a group of the formula: -(R6)n-CO-R7 (wherein n is 0 or 1; R6 represents a methylene or an ethylene group; and R7 represents an alkyl, an alkoxy, an alkylthio group, an alkylamino group or a hydrogen atom); Z represents N-R8 (wherein R8 represents a nitro group, a cyano group, an alkylsulfonyl group, a tosyl group or an alkylcarbonyl group) or a group represented by the formula: C(CN)R9 (wherein R9 represents a cyano group or an alkoxycarbonyl group); and A represents an ethylene group which may be substituted with C1 to C3 alkyl, excluding organophosphorus compounds of formula (I) in which R1 and R2 are C1 to C4 alkyl groups, X is NH, Z is a cyanoimino group or a nitroimino group and A is an ethylene group.