The bee is 86.344 by 81.673 pixels. With a density of 1, this calculates to a mass of 141 physics units for mass.
The square is 50 by 50 pixels. With a density of 1, this calculates to a mass of 50 physics units for mass.
A Force (when continue applied) gives an acceleration :
acceleration = Force / Mass (because the first law says : F = m * a )
Conclusion: How bigger the mass (by a constant force), how less you see it moving.
Or: The same force has less effect on heavier masses.
The bee has more mass than the square, so it is not moved as much as the square is by the same force.
Thank-you for the informative answer. How may I change the bee so it can work in the same way as the square.
Edit: I changed the force/pixel and it worked fine! Thank-you!