**(A-E)** Monte Carlo simulations of the trajectories of larvae exhibiting positive thermotaxis using the statistical distributions for run duration, turn size, and turn direction exhibited by real larvae navigating 0.5 °C/cm temperature gradients with 17.5 °C start temperature. For wild-type larvae, each of these statistical distributions is explicitly dependent on the larva's heading as described in . To simulate the effect of negating specific aspects of behavioral strategy, we constructed a set of unbiased statistical distributions for run duration, turn size, and turn direction by pooling all run and turn statistics exhibited by wild-type larvae without separation into quadrants based on run heading.

**(A-C)** Simulated trajectories of larvae regulating only one aspect of behavioral strategy. In each case, we allowed the simulated larva's heading to generate the statistics for one aspect of behavioral strategy using the statistical distributions exhibited by real larvae, and used unbiased statistical distributions for the other two aspects of behavioral strategy. In each panel, the trajectories produced by 30 simulations are superposed (purple trajectories), and two randomly selected trajectories are highlighted in blue and red.

**(D)** Simulated trajectories of larvae that utilize all three wild-type distributions for run duration, turn size, and turn direction.

**(E)** Thermotactic movement of simulations with zero, one, two, or all three types of modulation of run and turning behavior, quantified as the mean drift velocity of each simulation as it crawls up temperature gradients. As expected, simulations with zero bias exhibit zero drift velocity. For comparison, the experimentally measured drift speed of wild-type larvae exhibiting positive thermotaxis is indicated in red. Each measurement represents the mean +/- one standard error. **(F)** Results of Monte Carlo simulations of the trajectories of larvae exhibiting negative thermotaxis using the statistical distributions for run duration, turn size, and turn direction exhibited by real larvae navigating 0.5 °C/cm temperature gradients with 40 °C start temperature taken from . As in **(E)**, thermotactic movement of simulations with zero, one, two, or all three types of modulation of run and turning behavior is quantified as the mean drift velocity of each simulation as it crawls down temperature gradients. For comparison, the experimentally measured drift speed of wild-type larvae exhibiting negative thermotaxis is indicated in red. Each measurement represents the mean +/- one standard error.

## PubMed Commons