Monarch caterpillars are the larval stage of the Monarch butterfly, known for their striking black, yellow, and white stripes. They primarily feed on the leaves of milkweed plants, which provide them with the toxins that make them unpalatable to predators. As they grow, these caterpillars undergo several molts, shedding their skin to accommodate their increasing size. After about two weeks, they will form a protective casing called a chrysalis, where they will undergo metamorphosis into adult butterflies. This transformation is a crucial part of their life cycle.