Thermotaxis parameters.

Individual second instar larvae were placed on large Petri plates (20 cm×20 cm) either with superposed spatial temperature gradient or spatially uniform temporal gradient and tracked using similar methods as described elsewhere [4], [24]. At least 20 animals were used for each measurement. Each measurement represents the mean +/− one standard error. On spatial gradients (0.3°C/cm), individual larvae were initially placed near 17°C, and their trajectories towards higher temperatures were analyzed. Thermotaxis speed indicates the mean rate of ascent up the temperature gradient towards warmer temperatures. Mean forward speed during periods of persistent forward movement was also measured. On temporal gradients, larvae were subjected to sinusoidal temperature waveforms, ∼20°C offset, ∼1°C amplitude, 6 min period. The frequency of turning decisions and the mean size of the first head sweep in each turning decision was quantified during both warming and cooling phases of the temperature stimulus. * and ** indicates case in which each statistic differs between warming and cooling at P