Betta fish started consistently trying to jump out of tank

[Navfish]

I have a 5 gallon cycled tank w live plants and a nerite snail. I have a heater and filter and I have had this betta for over 5 months now. This morning I heard the sound of him jumping (i have a lid) so i did a water change but he is still trying to jump out. I dont know whats stressing him since this isnt normal behavior.

 

[GaryE]

Insects flying in the room?
Something outside in the wider the room frightening him?

There's a good chance the answer isn't in the tank.