A website describing a mid-16th century Italian jeweled marten’s head at the Walters Art Museum describes one line of thought regarding the presence of this accessory in portraits of women:

“The marten was thought to conceive its young through its ears, free from sexual intercourse, and was thus associated with Christ’s miraculous conception. This symbolic meaning is indicated by the presence of the dove of the Incarnation on the creature’s snout. Such objects were fashionable in Europe during the sixteenth century. They also served as protective amulets for pregnant women.”

The medieval legend to which the Walters’ website refers is referenced in the story of Galanthis in Ovid’s Metamorphoses, and also in the Epistle of Barnabas. Although Isidore of Seville (Etymologies, Book 12, Chapter 3) asserts that “Falso autem opinantur qui dicunt mustelam ore concipere, aure effundere partum,” this legend continues to appear as a fact of natural history in medieval bestiaries (such as The Aberdeen Bestiary and a 15th century French bestiary [MMW 10 B 25, fol. 24v]), and is illustrated in the Queen Mary Psalter (see The Medieval Bestiary: Weasel).

This description seems to be a lot more realistic than the line of thought usually put forward by reenactors and/or costumers – that it is meant to attract fleas to the fur, rather than the wearer – a theory which appears (at the moment) on Wikipedia, as well as plenty of other websites. It does seem highly unlikely that wealthy women would wear an such an ostentatious accessory to advertise their personal vermin problems, though. It appears that the Italian word zibellino (pl. zibellini) may refer to most of the mustelids, and so may be a more appropriate term for this 16th century fashion accessory than “flea fur.”

• Portrait of a lady by Bernardo Luini, c. 1520-1525
• Portrait of a Roman courtesan by Parmigianino, 1530-1535
• Portrait of Eleonora Gonzaga della Rovere by Titian, c. 1536-1537
• Portrait of Camilla Gonzaga de' Rossi, Countess of San Secondo, with her sons by Parmigianino
• Portrait of a young woman by Moretto, 1540s
• Portrait of Claude de Châteaubrun de Beaune dame de Gouffier
• Portrait of Livia da Porto Thiene and her daughter Porzia by Paolo Veronese, c. 1551
• Portrait of Bianca Ponzoni Anguissola by Sofonisba Anguissola, c. 1557
• Detail from a family portrait by Giovanni Antonio Fasolo, 1560s
• Portrait of Queen Isabel de Valois
• Portrait of Angelica Agliardi de Nicolinis by Giovanni Battista Moroni, c. 1565
• Portrait of Frances Sidney, Countess of Sussex c. 1570-1575 (see detail)
• Una Gentildona Maritata Padovana and a lady in a white dress in Mores Italiae, 1575
• Portrait of a noblewoman by Lavinia Fontana, c. 1580 (see detail)
• Portrait of an unknown lady attributed to William Segar, c. 1595
• Gentildona Padoana, Album Amicorum of a German Soldier (LACMA M.91.71.60), 1595