movement of an object inside another moving object at high speed

The same way you can walk back and forth in an airplane going 600mph.

Or the same way you can walk across the ground on a planet moving a gazillion miles an hour.

The air in the bus is moving at 120 km/h, just like the bus driver.

Put an aquarium in the bus and watch the fish swim front to back. How? The water is at rest with respect to the bus.

It is called inertial frame of reference.

What's the buzz?

As string/M theory tells us, spacetime consists of many dimensions besides the three (or four) that we humans normally perceive. Some of these other dimensions are quite small. For us they are invisible. But to a tiny insect they are very useful.

As the insect moves its wings, a significant percentage of their surface area are moving through two or three of these other dimensions. These provide a firmer "grip" upon which the wing can push very hard against. This gives an insect much more motive power than, say, a dog. Even dogs with wings cannot fly as quickly toward the front of a moving bus as the insect. Although winged dogs with very short fur can fly better than, say, a flamingo of comparable size.

The complex aerodymic effects as the wings & air molocules interact with these tiny dimensions and our "normal" ones is what causes insects to have such erractic flights. They can not predict the force vectors and it causes them to dart one way and then another.

Also this effect of the wing cells flexing into, out of and curving around all the dimensions causes the annoying buzzing sound. It is much worse for the poor flamingo though, since its tiny ears are rattled so by the small dimensions! It's odd that it doesn't try harder to get off the bus at the next stop.

DNPMSL!!! And I concur, it's very odd the flamingo would stay on the bus under the stated conditions... But then, he IS a bird-brain, after all.

Because no one had a newpaper to kill it ?

It can't. It was an elaborate hoax done with mirrors and a stunt double, set up by the insect, just to mess with your head and show which of the two of you had the superior intellect.

"could fly much faster from back to the front even when the vehicle was moving at an average speed of 120 km/h."

The only reason you saw a difference in speed in each direction is most likely that the various air leaks will flow from front to rear creating a "wind" inside the bus. Without leaks, the insect's speed would have been equal in both direction assuming that the insect had the same motivation both way.

This is the same as the spacial-velocity rift premise. Stand at the front of the bus and throw a baseball. If you match the vehicle speed the ball will hang motionless for several seconds before falling to the floor. The insect is also under the spacial-velocity rift effect. Bob Einstein (Albert's cousin) predicted this.

You are wrong. The ball start falling as soon as it is released.

In all probability it would be an opical illusion. As the insect is flying forward, the backgroud of the land outside the window is going in the same direction of the insect, so it would 'look like it was going slow.

When returning to the back of the bus the insect is going against the flow of the background and appearing to be going faster.

If the bus was accelerating (he said, "average speed of 120 km/h" and not constant speed) then the air pressure in the back of the bus would be greater than at the front (objects at rest - or moving slower - including air - tend to remain at rest...). Essentially, our bouyant little bug would get an extra push from the air pressure.

Relativity?

From your perspective inside the bus, all people are moving zero speed, as the bug flys to the front, it is moving relative to you.

The people outisde the bus are also moving relative to you, that they are moving in the backwards direction.

If you remove the front and rear windows, the bug will enter the front Oh so happy that the windshield didn't wreck its day, move at air speed (relative to you) +/- whatever speed it was doing relative to the air, and hopefully exit the back of the bus.

If a bug comes in from the outside, it will decelerate from the speed outside to the speed inside due to wind resistance, or whatever it hits after entering the open window.

If the bug is a bee, then a different set of circumstances come into play.... as people generally don't want to be stung, especially those who can come into Anaphleptic shock (or however its spelt) and the relative point of view becomes a variable as people start waving hands and others start getting out of its way as it randomly changes direction (with the asistance of being hit, and getting quite angry)

The insect was probably drafting behind seat backs as she flew prow-ward in the bus . . . then whipping around each seat, one by one, whenever the bus driver negotiated a turn in the road.