Eye colour: the expression of the w gene is restricted to a line across the middle of the eye in wRacing-Stripe flies. The phenotype is variable; flies differ in the amount of pigmentation in the stripe, the width of the stripe, the position of the stripe, and the amount of pigmentation in the "unpigmented" dorsal and ventral regions of the eye.
An insertion of a P-element carrying a w construct causes the insertion-site specific wRacing-Stripe phenotype.