Ithomiini: the Atlantic Forest butterflies greedy for toxic plants

Mimicry is a widespread phenomenon in Nature, where some species imitate the morphological and chromatic patterns of others, benefiting from some form of protection due to this similarity with the model. Usually, the model has some physical or biochemical characteristic that makes it detestable to predators. In the case of butterflies, this is usually the presence of toxic substances (usually alkaloids) and/or unpalatable substances in the organism of the models.

In the Americas, there is an endemic tribe of the Danainae subfamily of Nymphalidae: the Ithomiini butterflies, around 350 species – many of them popularly nicknamed ‘glasswing butterflies’ due to the transparency of a large part of the surface of their wings – where the majority participate in mimetic rings among themselves and with other Lepidoptera, including the Heliconiinae subfamily and some diurnal moths.

In most cases, the mentioned toxic, (unpalatable) chemical compounds in the “bad-tasting” butterfly’s are taken up in the larval stage from the plants on which they feed. In the case of the “glasswings,” the plants used by the larvae are partly Apocynaceae (a source shared with the Danaiini tribe), but most feed on Solanaceae, a botanical family that includes popular vegetables such as tomatoes, potatoes, eggplant and 'giló'. However, many species sequester these alkaloid compounds as adults; males in particular suck alkaloids from the flowers and roots of shrubs, vines or small trees of the Asteraceae family or from the decaying leaves of Boraginaceae.

During a walk along one of the butterfly monitoring transects (a section of the Yellow Trail) that had recently been cleared for maintenance, I was able to observe over the course of a week how groups of several species of ‘glasswings’ congregated on the roots of an Eupatorium shrub (Asteraceae) – especially in the early morning and late afternoon – as exemplified in the photo. The species observed sequestering alkaloids from these exposed roots were the following: Episcada striposis, Episcada sylvo, Hypothiris ninonia daeta, Hypothiris euclea lapria, Ithomia agnosia zikani, Ithomia drymo and Pseudoscada erruca.

a group of at least six species of Ithomiini sucking coumpounds from the exposed roots of an Asteraceae (Eupatorium sp.) (© Jorge Bizarro)

Data: 17/08/21