Why doesn't a bug on your screen react to your cursor?

[harry ashburn]

any entomolgists here? why does a bug on your computer screen not react when i'm trying to chase it away with my cursor? Dont you think a big finger or arrow circling around you would scare you?

[Elvis]

Good question. I notice that insects are drawn to the light of a TV screen, but don't seem to react to changes on the screen. (But, if you try to swat them, they fly away.)