The Garden Bug: Feeding Monarchs
By Brenda Weaver
The adult monarch consumes nectar from flowers, minerals from mud puddles and liquids from fruits. To attract them to your backyard, leave out slices of banana, oranges or watermelon, and plant a variety of flowering plants. The monarch caterpillar (the larvae stage of the monarch butterfly) feeds only on the leaves of milkweed plants. From these it gains all the nutrition needed to change into the adult form.
Source: www.monarch-butterfly.com