N=2 supersymmetry of higher superspin massless theories

We present N = 2 supersymmetry transformations, both in N = 1, D = 4 Minkowski and anti-de Sitter superspaces, for higher superspin massless theories. It is noted that the existence of dual versions of massless supermultiplets with arbitrary superspin s may provide a basis for understanding duality in N = 1, D = 4 superstring theory. We further conjecture that the N = 1, D = 4 supergravity pre-potential together with all higher superspin s pre-potentials are components of an N = 1, D = 4 superstring pre-potential.