Mosquito
Mosquitoes of the genus "Toxorhynchites" never drink blood. This genus includes the largest extant mosquitoes, the larvae of which prey on the larvae of other mosquitoes. These mosquito eaters have been used in the past as mosquito control agents, with varying success.
Gyrostigma rhinocerontis
Gyrostigma rhinocerontis (also known as the Rhinoceros stomach botfly) is the largest fly species known in Africa. It is a parasite of the Black Rhinoceros and the White Rhinoceros.