Ants can be killed by moving directly into them, but watch out for your tongue above when you are in the lower part of the anthill. Ants can only be killed by the tip of your tongue, and if they hit the extended part you lose a life.
Worms cannot be killed head-on, but cause no damage when they hit your extended tongue. You should move down below a worm or wait for it to pass, and then move in to eat it from behind.
Spiders can only be killed by eating a Queen Ant. This will destroy all insects on the level, removing any imminent danger. Spiders move across the top tunnel of the screen until they reach the middle, and then walk down your tongue, until they reach the tip which causes you to lose a life.
Try to save eating the Queen Ants for as long as possible, until absolutely necessary to save you from a life-threatening situation.
Worms often appear at the same time as ants, and this will make killing them difficult. Also, you have to be careful the ants do not hit the tongue. You must move the the row below them and cut round behind them, as eat them both before the ant makes contact with the extended part of the tongue.