What is the difference between worldsheet supersymmetry and spacetime supersymmetry? For worldline formulation of fermions quantum mechanics, there is a supersymmetry. But the corresponding spacetime theory (namely, QFT) is totally void of supersymmetry. Now to have fermionic excitations for strings, we need to add supersymmetry to the worldsheet, then how does the worldsheet supersymmetry induce spacetime supersymmetry?