WHat do you mean knock it off the raised platform??? WHich ant are you reffering to
It's been a year since I wrote this so I'm not totally certain, but if I remember correctly there is an ant in the upper right-hand corner of the room (which you can reach using the moth form) that is walking on a semisolid platform. Bumping it off the semisolid and onto the floor below should make its attack send you where you want to go, I think?