Tracking movement and gene expression of multiple flies using GFP. Multiple male flies were placed in a vial and tracked simultaneously for 48 hours. Black/white bars indicate the light/dark cycle the flies were cultured under prior to the beginning of the experiment. Activity is expressed as distance moved per hour (cm/hr), and GFP intensity is expressed as average pixel intensity per hour. 3xP3-GFP, transgenic strain I4, 1 day old (Blue). hsp70-GFP, transgenic strain 2MI4, 1 month old (Brown). hsp22-GFP, transgenic strain 1MI1, 1 month old (Black).