The former usually feed on Asclepiadeae, the latter on Solanaceae or Scrophulariaceae.
The two species figured, though belonging to such distinct and even remote genera, have acquired almost identical tints and markings so as to be deceptively alike.

The surface of the wings is, in both, transparent yellowish, with black transverse bands and white marginal spots, while both have similar black-and white-marked bodies and long yellow antennae.

Dr.Mueller states that they both show a preference for the same flowers growing on the edges of the forest paths.[105] We will now proceed to give the explanation of these curious similarities, which have remained a complete puzzle for twenty years.
Mr.Bates, when first describing them, suggested that they might be due to some form of parallel variation dependent on climatic influences; and I myself adduced other cases of coincident local modifications of colour, which did not appear to be explicable by any form of mimicry.[106] But we neither of us hit upon the simple explanation given by Dr.Fritz Mueller in 1879.
His theory is founded on the assumed, but probable, fact, that insect-eating birds only learn by experience to distinguish the edible from the inedible butterflies, and in doing so necessarily sacrifice a certain number of the latter.

The quantity of insectivorous birds in tropical America is enormous; and the number of young birds which every year have to learn wisdom by experience, as regards the species of butterflies to be caught or to be avoided, is so great that the sacrifice of life of the inedible species must be considerable, and, to a comparatively weak or scarce species, of vital importance.

The number thus sacrificed will be fixed by the quantity of young birds, and by the number of experiences requisite to cause them to avoid the inedible species for the future, and not at all by the numbers of individuals of which each species consists.