I did some checking around, and though it seems sometimes bug stains eventually fade away, it's probably best to address them immediately.
You might try dabbing a little with a soft cloth any of following:
- Isopropyl Alcohol
- A solution of distilled white vinegar with water (about 1:1 to 1:3) -- this is also good for water deposits, by the way.
- You could also try Wesley's Bleche-Wite on a soft cloth, and rinse/wipe with a separate sudsy damp cloth.
- Meat tenderizer (I'm guessing liquid), colorless, with water
I have not tried any of these, but they sound sensible and I'd probably try them before I'd try anything abrasive.