Perry's Index to the Aesopica
Perry reserves 424 for a joke reported in Diogenes Laertius, Vitae
Philos. II.5.42: Aesop once said to the dwellers
in the city of Corinth, 'Judge not virtue by popular standards.'
(Socrates is the supposed source of this report.)
You can find a compilation of Perry's index to the Aesopica in the gigantic appendix to his
edition of Babrius and Phaedrus for the Loeb Classical Library
(Harvard University Press: Cambridge, 1965). This book is an absolute must for anyone interested
in the Aesopic fable tradition. Invaluable.