The subject is from one of Aesops’ fables. The fox first invites the heron for dinner, but serves the food on a plate that the bird with its beak cannot eat from. The heron then invites the fox to a meal, and the embarrassed fox can only watch as his friend eats the fish from the narrow-necked vessel. The moral is: the trickster must expect trickery in return, and the golden rule of conduct is to do to others what one would wish for oneself.