While silk mechanical properties were affected by protein deprivation in four of the five species of spider (the exception being L. hasselti), the mechanisms by which the mechanics were affected differed in each instance. Our amino acid composition analyses, for instance, found a lowering of proline, alanine and glycine compositions in the silk of A. keyserlingi when protein deprived. Nevertheless the silks of N. plumipes and P. graeffei had greater proline compositions when protein deprived. Our genetic expression analyses revealed that most spiders seemed to preferentially regulate their expression of the MaSp1 genes rather than MaSp2 genes across treatments, contrary to what might be predicted, given the MaSp2 protein is expected to be the more costly of the two proteins to metabolically synthesize .