Act88F⁶ heterozygotes bearing one copy of Act88F^+tMa do not present obvious defects in average body weight nor in the development, morphology or thin filament lengths in indirect flight muscle, but present the following defects in flight performance, as compared to controls: a significant decrease in flight index assessed by standard flight assays; significant decreases in overall and angular velocity and significant decreases in centripetal, but not overall, acceleration, assessed by digital inline holography. Act88F⁶ homozygotes bearing two copies of Act88F^+tMa are flightless but do not present any obvious defects in the development, morphology or thin filament length in indirect flight muscle