The invention relates to novel substituted carbodiimides of the formula ##STR1## wherein R.sub.1 is hydrogen, halogen, C.sub.1 -C.sub.10 alkyl, C.sub.1 -C.sub.5 alkoxy, C.sub.1 -C.sub.5 alkoxy which is substituted by 1 to 7 halogen atoms, or is C.sub.1 -C.sub.5 alkylthio; PA0 R.sub.2 is hydrogen, halogen, C.sub.1 -C.sub.10 alkyl or C.sub.1 -C.sub.5 alkoxy; PA0 R.sub.3 is hydrogen, C.sub.1 -C.sub.10 alkyl, halogen, phenoxy, phenylthio, or is phenoxy or phenylthio, each mono- or disubstituted by a member selected from the group consisting of halogen, methyl, ethyl, C.sub.1 -C.sub.3 haloalkyl containing 1 to 7 halogen atoms and cyano, or is pyridyloxy or pyridyloxy which is mono- or disubstituted by a member selected from the group consisting of halogen and C.sub.1 -C.sub.3 haloalkyl containing 1 to 7 halogen atoms; PA0 R.sub.4 is C.sub.1 -C.sub.12 alkyl, alkoxyalkyl containing a total of 2 to 10 carbon atoms, C.sub.3 -C.sub.10 cycloalkyl, C.sub.3 -C.sub.10 cycloalkylmethyl, C.sub.3 -C.sub.10 cycloalkyl which is substituted by 1 to 3 C.sub.1 -C.sub.3 alkyl groups, or is C.sub.1 -C.sub.5 -alkyl which is substituted to 1 to 2 C.sub.3 -C.sub.10 cycloalkyl groups, or is a polycyclic alkyl group containing 7 to 10 carbon atoms, phenyl(C.sub.1 -C.sub.5)alkyl or phenyl(C.sub.1 -C.sub.5)alkyl which is mono- or disubstituted at the phenyl nucleus by halogen, trifluoromethyl, methoxy or ethoxy, to the preparation of these compounds and to compositions containing them for use in pest control, especially for controlling insects and representatives of the order Acarina that attack plants and animals, in particular plant-destructive sucking insects.