The scent-tracking mode used here seems to be a sort of variant, in which the long legs are not chosen randomly.
WRT the insect density decreasing as some fly away: in reality, others will arrive at approximately the same rate, keeping the density approximately the same, so it is probaby more realistic to put a box around the simulation, e.g. by reversing the direction of those that have moved away to the point that they would be several time-slices away from entering the window even if they flew back in a straight line.
The scent-tracking mode used here seems to be a sort of variant, in which the long legs are not chosen randomly.
WRT the insect density decreasing as some fly away: in reality, others will arrive at approximately the same rate, keeping the density approximately the same, so it is probaby more realistic to put a box around the simulation, e.g. by reversing the direction of those that have moved away to the point that they would be several time-slices away from entering the window even if they flew back in a straight line.