Ithomiines are unpalatable because their adults seek out and sequester pyrrolizidine alkaloids from plants that they visit, especially composite flowers (Asteraceae) and wilted borages (Boraginaceae).

The local abundance of ithomiine butterflies in the Amazon forest, the lack of observations of predation, and their "peculiar smell" led Henry Walter Bates in 1867 to suggest that these organisms should be chemically defended.

This was first experimentally demonstrated in 1889 when Thomas Belt fed ithomiines (that he called "Heliconii") to birds, the spider Nephila, and the white faced monkey Cebus capucinus.

Besides, João Vasconcellos-Neto and Thomas M. Lewinsohn demonstrated that the Neotropical orb-weaving spider Nephila clavipes released unharmed 14 species of field-caught ithomiine butterflies.

Other butterfly and moth species that sequester pyrrolizidine alkaloids (Danainae, Ctenuchidae, and Arctiidae) also visit similar sources.

The subtribes in the Ithomiini help to organize the 43 recognized genera, but this group is the subject of ongoing molecular, phylogenetic and morphological research, and the classification presented below will no doubt be refined in the near future.