The need to feed sundews apparently varies depending on the species. My understanding is that they extract mineral nutrients from their prey to augment what little they might get via their roots in their normal habitat. So basically the bugs are "fertilizer". While they do photosynthesize, that's how plants make energy food from sunlight, that's not the same thing as providing them with nutrients via bugs (or roots). I've read of people using a certain kind of fish food and other things to feed sundews that do need feeding where they can't capture enough bugs. This article on the topic may be of interest:
http://www.growsundews.com/fee...
