Seasonal dynamics of amount of asymmetric individuals on sternopleural bristles (SB) and arista branches (AB) numbes was investigated. It was shown, that this value increased from spring to summer and decreased from summer to autumn. Statistically significant negative correlation between of amount of AB-asymmetric individuals and number of AB, and positive one between asymmetry and variability of number of AB was obtain. Seasonal dynamics of amount of asymmetric individuals determined by dynamics of phenotypic structure it on both meristic characters, it is has been proposed possible action of natural selection.