whatever you feed them. make sure is a live insect. venus' flytraps have small trigger hairs inside their trap Lobes.
they have about 5 to 6 trigger hairs in total.

when an insect walks inside a trap, it must touch the trigger hairs atleast twice in order for the trap to close. after it closes, the inscet begins to struggle, this struggle will stimulate the trap to shut tighter and tighter. after it shuts completely, the trap begins secreting digestive juices to digest the nutrients from the insect pray. about 10 days after digesting its pray, the trap will re-open and only the exoskeleton of the insect will be left behind inside the trap.

Never feed a venus' flytrap animal meat, this has been known to cause the plant's trap and leaf to rot.

make sure to use live insects if you want a venus' flytrap to completely digest a prey. if a dead pray is only dropped inside the traps, chances are that the traps will re-open and the inscet will not be digested. the traps re-open in about 24 hours.

you can obtain live crickets or live maggots at local petshops. you can use tweezers... to feed the plant.

You don't need to feed them at all. Even if they don't catch any insects before going outside after frost has past they will be just fine.

Tom

Baby crickets from your local pet shop would be great. Put them in the fridge for a few minutes to slow their metabolism down and then place the sleepy critter in the trap. They wake up and struggle and the VFT tightens. I know this is for educational purposes, but as said earlier, they don't need to be fed purposely.

yup, I agree with the masses... live bugs. Crickets are a good choice because they are easy to get at pet stores. If you want the crickets to be a bit more dosile when trying to grab them for the plants, I once read something that may help. Stick them in a freezer for a minute. You don't want to leave them in too long because it may kill them, but since they're cold blooded, they slow down when exposed to the cold. (sure beats having crickets jumping all over your house) They should stay stunned for a few minutes at least while you feed them to your plants.

Here is a link that might be useful: Aracknight's Deadly Delights