A group of conservation organizations teamed up with a leading monarch butterfly scientist on Tuesday to petition. Most monarch caterpillars breed in the Midwest, and feed off of milkweed. While Roundup doesn’t kill genetically. MACKINAC ISLAND, MI — A new grassland habitat area has been established on Mackinac Island to aid the migratory North American monarch butterfly population. About 400,000 common milkweed seeds. found "no relationship". and subdivisions and widespread…