A: The life span of butterflies varies according to the butterfly. Larvae generally live longer than the adults. The longest life spans are associated with the migrating Monarchs, Mourning Cloaks, and some moths which can live for about 6 to 12 months. The caterpillar of the monarch butterfly feeds only on milkweed. The caterpillar of the mourning cloak feeds in groups on the leaves of deciduous trees, including the willow, elm, hackberry, cottonwood, poplar, rose, birch, hawthorn, and mulberry. The adult mourning cloak butterfly feeds on tree sap and rotting fruit. It may also eat nectar from flowers. The shortest butterfly life spans are found among the Coppers and Small Blues butterflies which live in their adult state for only a few days!