There's a lot of things going on with this, but the gameplay is fairly straightforward at least. The music was pretty loud from the get-go, and ideally you'd want a way to turn it down/off, or at a minimum edit the sound file so it's not so loud.
The explosion animations are nice, but generally the art styles don't seem to match up with each other. Especially the weird hair/brainy thing on the intro screen. It's just an odd match-up for me.
I also felt the missiles could've been used better, like click on them and then click where you want the explosion to occur. Otherwise you just have to wait for bugs to gather near the button.
I do hate flies though, so it always amuses me to destroy them. Keep it up!