The Molecular Age has given taxonomists many new characters for the reconstruction of phylogenies (evolutionary history). The changes to DNA (through descent with modification) leave patterns such that those groups most recently separated have a greater proportion of DNA in common. DNA from mitochondria has characteristics that are very useful for constructing phylogenies. Complete mitochondria DNA sequences are a published for over 100 species of butterflies and more are expected.
The molecular data from the DNA sequences clearly indicates that the Swallowtails (Papilionidae) not the Skippers (Hesperiidae) are the group most closely related to the moths. The Skippers are descended from the Swallowtails in their own branch of the phylogenetic tree. The other branch leads to all the other butterfly families. This analysis firmly embeds the Skippers within the butterflies. The biology of the Skippers is best understood as one of several families of butterflies.