The body mass of banEPg30491/Df(3L)banΔ1 adults is only 84% of that of control flies. These flies show 76% viability. The body mass of homozygous adults is only 85% of that of control flies. These flies show 60% viability. The wing blade area of banEPg30491/Df(3L)banΔ1 flies is only 90% of that of controls. This decrease is entirely due to a decrease in the number of cells, and is not due to a decrease in cell size. Expression of banEPg30491 under the control of Scer\GAL4en-e16E results in a significant increase in the ratio of posterior:anterior area of the wing compared to control wings. There is no increase in overall wing size.