Monarchs lay their eggs singly on the underside of leaves and sometimes on the flowers of different milkweeds (Asclepidaceae:Asclepias). Recent analysis of genomes of migratory and non-migratory monarchs shows that monarchs originated in North America from a migratory ancestor.
The first instar larva is white with a black head. The larva develops a more conspicuous striated yellow-and-black coloration in the second instar. This coloration varies depending on subspecies in mature larvae. Larvae also develop two thoracic and two abdominal dorsal filaments.
Development from egg to adult takes less than a month. In North America, the monarchs go through at least four generations a year before they start migrating south in the fall. View the amazing monarch butterfly here!