High Quality Content by WIKIPEDIA articles! Milkweed butterflies are a subfamily, Danainae, in the family Nymphalidae, or brush-footed butterflies. They lay their eggs on various milkweeds on which their larvae (caterpillars) feed. Historically, this group had been considered a separate family, Danaidae, and the tribes placed herein were sometimes considered distinct subfamilies in the Nymphalidae.