Not half bad.
I personally enjoyed this. It was a nice distraction from work. I would have liked to see more level of interactivity, such as being able to pick up and use the objects on the screen. Especially since the ants can actually crawl under them. Maybe a toolbar with some things on it. A magnifying glass, perhaps. Or a brick.
I would also request a respawn rate. I killed a fair bit of ants and no more were showing up.
My only other suggestion is to reduce the size of the glaring banner. Which, by the way, the ants can crawl on and are immune to my squishing.