Milkweeds are named for their milky, latex sap which oozes from the stems and leaves when plants are injured. The milkweed plant plays a critical role in the monarch life cycle. Monarch butterflies only lay their eggs on the underside of milkweed leaves and no other plant species. Caterpillar larvae mature and emerge from eggs after three to five days. The caterpillars feed on milkweed leaves, which provide them with a chemical defense. The larvae ingest and sequester toxins from milkweeds including the stems and leaves. These toxins protect Monarch butterflies from predation as the caterpillar becomes toxic to potential predators. Milkweed bugs, beetles, and aphids also use the plant and feed on leaves, flowers, and seeds. Milkweed stalks once the plant died back in the fall or winter.