Regardless of any advice found anywhere else on the internet, i advise you not to feed your Venus Flytrap.
You are not God. Do not play havoc with his plans. Natural selection is important for every species survival. The plant is more than capable of catching it’s own flies or bugs, even on an isolated windowsill.
Also after a few closures the trap will retire. This doesn’t look great and is a waste of what could have been a great trap.