The substituted spirodilactam of the invention includes those of the formula I ##STR1## wherein Q is --CN or is --C(O)Y in which Y is chlorine or bromine, or Y is OY' in which Y' is hydrogen, a salt-forming cation or an unsubstituted or inertly substituted aliphatic or aromatic group of from 1 to 20 carbon atoms, or Y is N(Y)2 in which each Y independently is a hydrogen atom or an unsubstituted