Milkweeds (Asclepias sp.) are an important nectar source for bees and other nectar seeking insects, and a larval food source for monarch butterflies. Milkweed is named for its milky juice, which contains alkaloids, caoutchouc, and several other complex compounds including cardenolids. Some species are known to be toxic. Species in the Asclepias genus grow their seeds in pods. These seed pods contain soft filaments known as either silk or floss. The filaments are attached to individual seeds. When the seed pod ripens, the seeds are blown by the wind, each carried by several filaments.