I just bought a Venus fly trap a few days ago. My new Venus fly trap won't close ANY of its little traps. I put an ant into it and none of the traps closed.
Is this natural?
Venus fly traps have trigger hairs (which are visible to the naked eye) inside their mouths. In order to trigger their mouths to shut, the prey (or yourself) must trigger two or more hairs within a certain small time frame (35 seconds). If the hairs aren't continually triggered after the mouth has shut, then the mouth will open back up after a short while. If you think about it, this is sensible because their is no nutritional value to, say, a small leaf that has blown inside a trap.
Interesting trivia taken from http://www.flytrapcare.com:
I used to keep Venus Fly Traps, just a few heads up:
ADDED: I used to get dead flies, put them inside the VFT mouths and manually trigger the hairs with a needle. Once the trap springs close, I'd apply a light pressure to the trap with my fingers to simulate a struggling insect so that the trap will stay closed. Much easier than trapping a live insect!