@globalmuseum
Adults of Hoverflies are not predators, they are pollinivorous/nectarivorous and very important as pollinators. Larvae of some subfamilies are instead great predators of aphids but not all Syrphidae.
Best adult predators in flies are robber flies (Asilidae), dagger flies (Empididae), and long-legged flies (Dolichopodidae), but Asilidae prey big insects. Dagger and long-legged flies prey mosquitoes and other midges often.