Environmental protocols used to study temperature entrainment in the context of continuous increases or decreases in absolute temperature. Different environmental protocols were used as indicated. First, flies were entrained to three 12-h light/12-h dark cycles at one of several phases as indicated by the white/black bars at the bottom of the panel. Next, they were subjected to a 4-day temperature regimen that superimposed a continuous temperature increase or decrease (3°C per day) on either otherwise constant temperature (ramp up or down) or daily temperature gradients with a range of 1.5°C (step up or down) or 4°C (zigzag up or down) (see Additional file 2). Note that the composite temperature profiles each show a range of 3°C on each consecutive day. Finally, the flies were released into free run at 17°C or 29°C in constant darkness. Each temperature protocol was combined with the light/dark protocols indicated below it, with the exception of 'step down' which was combined with four of the five indicated light/dark profiles (9:00 to 21:00 light phase was not used).