​Monarch SOS is a butterfly, caterpillar and milkweed identification guide suitable for all ages. The app includes similar species often mistaken for monarch butterflies, chrysalises, caterpillars and eggs, as well monarch larval instar identification. Also included are milkweed species photos and profiles for users to be able to correctly identify monarchs' larval host plants. The app is used by citizen scientists who participate in the popular Xerces Society Thanksgiving count and the Western Monarch Milkweed Mapper (WMMM), as well as to record tagged monarchs, report tags, and report adult monarchs to the Southwest Monarch Study.