No.

When the fly is on the air, it’ll be pushing air downwards (while pushing itself up). If it were to be floating without vertical movement, the force of the air being pushed down will be equal to the weight of the fly, meaning the scale will keep its reading static irrespective of whether the fly is flying or sitting on the scale. However, if the fly is flying upwards, the scale will show an increased weight, as the force acted upon the air will be higher than the weight of the flight (in order for it to “beat” gravity). Conversely, if it’s flying downwards, the scale will measure a bit less.