We performed the following tensile tests under controlled temperature (~25°C) and humidity (~50% R.H.) in still air within 10 days of silk collection. We placed each of the cardboard frame-mounted silks for each species within the grips of an Instron 5543 tensile testing machine (Instron Machines, Melbourne, Australia) with a ~2μN resolution . We ensured that the grips held the silks firmly at the upper and lower frame edges. The left and right sides of the frames were cut away and the silks stretched at a rate of 0.1 mm s-1 until the fiber ruptured.