  The muon and tauon light-by-light scattering contributions to hyperfine
splitting in muonium are calculated. These results conclude calculation of all
hard three-loop contributions to hyperfine splitting containing graphs with
closed fermion loops. We discuss the special role that the lepton anomalous
magnetic moments play in these calculations. The full result for all three-loop
radiative-recoil corrections to hyperfine splitting generated by the graphs
with closed lepton loops is presented.
