International audience The medieval texts examined here illustrate the encounter of natural science and spirituality regarding the spontaneous mode of procreation of "vermin". This scientific information has been accepted and popularized since antiquity, repeated without discussion during the Middle Ages and revived during the golden age of medieval encyclopedicism in the first half of the 13th century, before being discussed at length by Albert the Great on new Aristotelian and Avicennian scientific bases. From then on, the "worm" diversified into various ringworms, whose modes of reproduction and generation were increasingly specified and defined, thanks to new philosophical material which also fed university education from about 1240 onwards. In the Christian tradition, the pattern of the conception of the worm, an imperfect animal, gave also rise to a positive exegesis related to the son of God, Christ. To be possible, this interpretation carried by the first Fathers of the Latin Church had to be based on a shift in value: leaving the corrupted humidity, the abject insect was born clean from the "pure earth" assimilated to the Virgin (in Maximus of Turin and in Augustine, taken over by Cassiodore). Between "cursus rerum" and "natura rerum", the miracle took place and associated spontaneous generation, human generation, creation and divine incarnation. Without being the predominant tradition, this patristic tradition found an illustrious Carolingian defender in Jean Scot, and was disseminated by the Glossa ordinaria, then relayed by Peter the Lombard in the twelfth century. However, it remained in competition with the less flattering naturalistic interpretation, which allowed the insect to appear in human or earthly fertile corruption.