a–c For border interactions, the angle of heading is predictive of the angle of escape. a Schematic of the analysis. The heading angle is quantified in relation to the isothermal lines of the cool/hot boundary while the escape turn is categorized as “left” (green) or “right” (purple). b Distribution of left/right escape turns (binned in 45° intervals) as a function of initial heading angle. c Inter-antennal differences >0.1 °C are predictive of escape turn direction (prediction accuracy, bootstrap mean ± STD). d–f Surgical removal of the left (d) or right (f) antenna biases escape turn direction towards the side of the lesion (GLMM, Wald Test, Pleft = 6.3e−5, Pright = 9.3e−4), while removal of both antennae (e) abolishes left/right bias (GLMM, Wald test, Pboth = 2.1e−4). g Stochastic loss of the Gal4 inhibitor Gal80 produces flies in which either the left or right hot TRNs of the arista are genetically silenced and, at the same time, labeled by GFP expression (representative 2-photon stacks of TRN axon terminals are shown to the right, labels are the corresponding genotypes). h–j Stochastic silencing of either left or right hot TRNs (or both), produces a distribution of turning angles similar to that obtained from surgical ablation ((i) is the control genotype with bi-lateral silencing, see corresponding panel in (g)) (In all panels N denotes the number of animals, GLMM, Wald test, Pleft = 9.0e−6, Pright = 2.1e−2; Pboth = 2.5e−5). Note that mosaicism was determined by post-facto dissection and imaging.