  We discuss a Hamiltonian reduction procedure that relates the mechanics of an
N=2 particle on CP^3 with the motion of such a superparticle on S^4 in the
presence of an instanton background. The key ingredients of the bosonic
fibration S^2 -> CP^3 -> S^4 are recalled from the viewpoint of particle
mechanics on CP^3. We describe an N=2 supersymmetric extension which allows for
a Hamiltonian reduction. The S^2 degrees of freedom are encoded in the
supercharges via SU(2) currents. Finally, we present the Hamiltonian of our
system and its superfield Lagrangian.
