I have a bug living on my basil stem and I suspect it's doing damage, but I'm not sure. It's thin, about a half inch long and it flies.

He's a clever little guy. If I get close to try to get a good look, he hides on the back side of the stem, aligning himself parallel with the stem so he's hard to see. As I move around the plant he moves with me to always stay behind the stem.

I think I saw him spraying something out of the top of his back near his hind section - is he sucking sap out of the stem and ejecting waste out of his back?

I tried spaying him with soap. He takes a couple of sprays and flies away - then eventually comes back.

What IS that thing and is he doing damage? And if so, how can I make him suffer for it?

I know it's hard to identify by just a description. I'll post pics if I can get them.