In the 1D arena, adult flies can walk either in a forward or backward direction. Two LEDs, one blue and one red, are positioned in the middle of the track. Flies can not see the red light so the idea is to compare the avoidance or attractive behavior of flies depending on heat effects. We want to control/test if the blue light avoidance of pan-neuronal ChR2 transgenic flies is due to heat effects or to light activation of the channel. We measure previously the light intensity related to the heat increase for each LEDs so we can now use the red light as a heat effect control.