Hi. I will be staying in Varenna but want to dine at least once in Bellagio and enjoy Bellagio into the evening. The scheduled ferry service does not run late into the evening, so I am hoping that there are water taxi's available in Bellagio to take me back to Varenna. Anyone know if they exist, until how late in the evening, and approximate cost? To be clear- I'm not asking about the ferry service, nor a "tour"- just transportation back to Varenna at e.g. around midnight.
Yes. There are several taxi boats that I have seen.
Generally they offer longer excursions, since for such short hop, people use the frequent public ferries, however I'm sure they would be available for shorter transfers too.
http://www.lakecomo.it/en/getting_around/taxi_boat
Ask the staff at your hotel. If there is a service that operates that late, they'll know about it. You may have to return to Varenna a bit earlier.