[Hussell]

Nowhere in the paper does it say that individual spiders are varying their silk composition in response to conditions. The selective expression of proteins is a difference between the two species studied, not between individuals within one species.

The title is technically correct: the two species share a lot of glue genes, and the properties of their silks differ due to other genes affecting things like the ratios of glue proteins in the silk, and those genes evolved faster than the glue genes themselves.

[MattPalmer1086]

Correct, although I'm not sure if they proved that other genes were responsible for the variation, just that the glue genes were essentially the same between them.