  We deduce a microstructure inspired model for humidity and temperature
effects on the mechanical response of spider silks, modelled as a composite
material with a hard crystalline and a soft amorphous region. Water molecules
decrease the percentage of crosslinks in the softer region inducing a variation
of natural configuration of the macromolecules. The resulting kinematic
incompatibility between the regions crucially influences the final mechanical
response. We demonstrate the predictivity of the model by quantitatively
reproducing the experimentally observed behavior
