The Ants.

 + There are ants. Do you see them?

- No. Where?

+ Right here! There's a whole gang of them.

- I don't see anything there.

+ We can't let them in the house. They'll just multiple and they'll take over!

- Go outside and take a break. Sit in the sun and drink some water or something.

+ I did that! Are you saying you don't believe me?

- I'm not saying I don't see what you're seeing. 

+ Look closer. Pay attention.