We have officially hit the “-ber” months, and that means fall is in the air. In Indiana, it also means that monarch butterflies will begin to make the long journey across the Hoosier State in search of warmer weather. Why Monarch Migration MattersAll across Indiana and the Midwest, monarchs are already forming migratory roosts. Get our free mobile appTypically, during the fall migration, millions of monarchs will make their way through Indiana on the long and arduous journey. In Mexico, monarchs roost in oyamel fir forests, which occur in a very small mountainous area in central Mexico.