An aetiological myth is one which is regarded as having been invented ex post facto to explain some fact, name or coincidence, the true account or origin of which has been forgotten.
These are clearly aetiological, and invented to explain an existing custom, which the church had adopted from its pagan medium.
Five main cycles of story may be distinguished: (1) the foundation of the citadel Cadmea by Cadmus, and the growth of the Sparti or "Sown Men" (probably an aetiological myth designed to explain the origin of the Theban nobility which bore that name in historical times); (2) the building of a "seven-gated" wall by Amphion, and the cognate stories of Zethus, Antiope and Dirce; (3) the tale of the "house of Laius," culminating in the adventures of Oedipus and the wars of the "Seven" and the Epigoni; (4) the advent of Dionysus; and (5) the exploits of Heracles.
It is doubtful whether the distinction drawn between pestis minor and pestis major has a real aetiological basis.
It is impossible to trace a safe path through the complicated aetiological myths, the fragments of reshaped legend and tradition, or the adjustment of rival theologies.