Fig. 7. Breaking force (F_max) scales with mass, (M), as F_max=11.2M^0.786, r²=0.96, s.e.m. of the slope=0.027 for A. diadematus, and as F_max=0.363M^0.66, r²=0.87, s.e.m. of the slope=0.13 for S. scenicus (solid lines). The pre-web first-instar A. diadematus were excluded as outliers and fall well below the extended best-fit line (dotted line). The static safety factor (S_BW) determined from the force-mass scaling relationship, is shown as broken lines, where the black line indicates data for A. diadematus (S_BW=1.14M^–0.214) and the blue line indicates data for S. scenicus (S_BW=0.037M^–0.340).