A study done by researchers at Iowa State University’s Department of National Resource Ecology, Management, and Entomology indicates female Monarch butterflies have a preference for certain Milkweeds to lay their eggs on. Survival rates of the Monarch caterpillars feeding on the species of Milkweed they hatched on also indicate what the best Milkweeds were. The top three species include Swamp Milkweed (Asclepias incarnata,) Common Milkweed (Asclepias syriaca,) and Prairie Milkweed (Asclepias sullivantii.)