odd behavior- climbing the walls

My cat Malachy has recently been exhibiting a very odd behavior lately ...he sits and watches the walls, meows & claws at them, as if trying to climb or attack something. He gets pretty agitated at times ...and it's becoming a nuisance  as well as a concern.  He is very excited by little insects & I know this is the time of year they are getting in but I don't see anything. Nothing has really changed in the household that should be upsetting him.  I am planning to begin moving soon, but have done no packing or other signs of the impending change.  Is he 'acting out' in some way, or is this just a silly quirk he has developed ...maybe he sees(or hears) things I don't ??

Ritz does the looking at the wall behavior sometimes. I tend to think it's a tiny insect only she can see/hear. Movement of any kind catches cats' attention.
Any possibility there are bugs/mice/chipmunks inside your walls? Yeah, I know: horrors!
Remember, cats have much much better hearing than us humans.

Yeah, my cats do that too. We have some fruit flies in the kitchen that I can't get rid of. My cats go nuts when one flies low enough. They'll literally jump 3 feet vertically up a wall. I just think it's funny!

that's probably what it is ...I don't think there is anything gin the walls but I have seen a fruit fly now & then - those are pretty small ...I just hate having him mar up the walls since I'm renting ...I guess that's what my pet deposit is for lol!