By Newton's third law, force on bug and vehicle will be same when they collide with each other irrespective of their masses.
But according to Newton's second law, force is mass times acceleration. Since the force on each mass is same, the smaller mass will accelerate more and the heavier mass will accelerate less for the same force.
Therefore the acceleration of bug will be very greater than vehicle as the mass of the bug is very small as compared to vehicle.
When a boy throws a ball and accidentally breaks a window, the momentum of the ball and all the pieces of glass taken together after the collision is THE SAME as the momentum of the ball before the collision
