On the other hand, Sabina Magliocco in her article Spells, Saints, and Streghe: Witchcraft, Folk Magic, and Healing in Italy (2000), managed to answer the question rather neatly. So I am going to quote her:
It is clear that many activities attributed to witches were folkloric in nature--that is, no living member of any community, even traditional magic-workers, practiced them. Following Davies' recent work on witch belief in Britain (1999), I call these the province of the folkloric witch--the supernatural figure of legends and folktales. The word strega (plural streghe), from the Latin strix, "screech-owl," is often used in Italian to refer to the folkloric witch, and the word has ancient negative connotations. Pliny the Elder wrote about striges (plural of strix), women who could transform into birds of prey by means of magic, and who would fly at night looking for infants in their cradles to slaughter (Pliny the Elder, cited in Cattabiani, 1994:207-208). The strega therefore is not just a bogey created by the Inquisition, but a dangerous character with deep roots in Mediterranean folklore.
The folkloric witch appears predominantly in legends (accounts about supernatural events that were told as true) and folktales (purely fictional accounts set in a magical world). In Italian folklore she is usually female. Folkloric witches perform feats that are obviously supernatural: they can transform into animals (wolves, hares, lizards and cats are popular choices), fly through the night sky on the backs of animals, tangle people's hair in their sleep, steal milk from nursing mothers and livestock, suck blood from living beings, and torment their enemies by paralyzing them in their beds at night (DeMartino, 1966/83:71; cf. Hufford, 1982). Folkloric witches' activities sometimes overlap with those of fairies and the dead: in Italian folklore, noisy night raids and circle-dancing in the cemetery or church square are attributed to all three.
Clearly, the folkloric witch is fictional; she represents an embodiment of rural peoples' worst fears, and her actions do not correspond to any real folk practices documented by ethnographers. Nevertheless, the presence of this character in Italian folklore from all regions indicates the ambivalent feelings villagers had towards those who practiced traditional magic and who just might be dangerous streghe.
Sabina Magliocco, Spells, Saints, and Streghe: Witchcraft, Folk Magic, and Healing in Italy Part 7 of 13: The Folkloric Witch, http://www.italiansrus.com/articles/subs/folkmagic_part7.html, accessed March 3, 2011. This article first appeared in The Pomegranate 13 (2000), pp. 2-22.
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