Variability of the hb border positions in the simplified model and the intersection points between the initial Hb profile and the attraction basin boundaries (from Fig. 5C) for two Bcd families and for the whole Bcd set, in comparison with the positional variability of threshold Bcd concentration. The Bcd threshold value for a family was chosen by picking a Bcd profile corresponding to the mean position of the hb border for that family; then, the threshold value was equal to the value of this Bcd profile at that position. The full range (f.r.) and standard deviations (s.d.) are given in % of embryo length. The standard deviation for the hb border is 1.3% in solutions of the full model and 1.0% in data .