This here is a picture I took of Black fly, later identified as the African hippo fly.
It can be easily confused with the black horse fly, but that is simply because they stem from the True Horse Fly insect Family (Tabanidae). The most prominent distinguishing factor, is the white/yellow spot on its back.
These flies prey on large South African mammals throughout sub Saharan Africa, by using a sizer like jaw or rather mouthpiece action to cut into the flesh, their favorite pray being hippo's - thus their common name, however the will also attack other large mammals, such as buck and cattle.
although this fly grows up to 4.6cm as an adult, these flies just like most other insects, start off as a tiny larvae. In the case of the Hippo Fly, these larvae reside in mud pools, where they feast on tadpoles and larvae of other insects.
Feel free to use this image as a stock image.