Not sure which species this fly is, but may be a Sarcophigid fly. At any rate, those "yellow slippers" it is wearing are the pollen sacs from a Common Milkweed plant. The insects land on the flowers to get at the sweet nectar and when they fly away, they find the sticky sacs attached to their feet. Landing on the next milkweed flower, they deposit the sacs and thus help with pollination. Sometimes, however, the flies and other insects that feed on the flowers become stuck and end up dying on the flowers. Or losing a leg or two.