Here we performed an examination of nutritionally induced MA silk property variation by running experiments similar to those described by Blamires et al. . However, we used five species of Araneoid spiders: Argiope keyserlingi, Eriophora transmarina, Latrodectus hasselti, Nephila plumipes and Phonognatha graeffei, and directly measured spidroin expression using quantitative real-time PCR (RT-PCR) techniques. Specifically, our experiments aimed to answer two persistent and problematic questions about spider silk property variability: (1) Do the silk nanostructures and mechanical properties of different spiders respond similarly to variations in spidroin expression? And (2) what are the relative contributions of changes to amino acid compositions and nanostructures in inducing spider silk mechanical property variation? To answer the first question, we performed silk tensile tests, SAXS/WAXS analyses, amino acid determinations, and gene expression analysis, for the abovementioned spiders and compared the results across species and treatments. To answer the second question, we pooled the mechanical property, nanostructural, and amino acid compositional data across species and constructed predictive models.