Response of body size and behavioural traits to selection. (a) Dry weight at eclosion, (b) Courtship frequency and (c) Mean activity score of selection regime males. Individuals were weighed in groups of five. An average body weight was calculated using the weight of the five flies. These mean values were taken as the unit of analysis. Mean activity score (see Methods section) and mean courtship frequency were calculated for each vial using the raw data and these were then used as the unit of analysis. Points not sharing common letter are significantly different (determined using Tukey’s HSD).