Battle of Ant Island was a battle and revolution of the Ants against the grasshoppers.
With the circus bugs agreeing to help the ants, they all begin work on a fake bird which should scare away Hopper and his gang for good. However, P.T. Flea arrives on the island and reveals that the new bugs are just circus bugs and not trained warriors. Distraught, Princess Atta banishes them along with Flik to go back to where they came from.
Dot catches up with the circus wagon, and soon persuades Flik and the others to return and help fight. Before they can do so, they tie up P.T. (using Rosie's web) and lock him in the back of the circus wagon. Flik, Dot and the circus troupe watch from a distance as the grasshoppers take the ants hostage and take all of the food. They decide that their first priority is to save the Queen, who is sitting next to Hopper.
Flik and Dot enter Dot's hideout and regroup with the scout ants. Meanwhile, the Circus Bugs entertain the grasshoppers, and put on a show. They lie that they were invited by Princess Atta as a surprise for the grasshoppers' arrival. At first, Hopper orders them to be squished. But after seeing Tuck and Roll's act, he decides that he may enjoy the entertainment. While the grasshoppers are distracted, Flik and the young scouts climb up the rocks behind the enemy and enter the fake bird they had made earlier.
During the circus acts, Manny asks for someone to join him as an assistant so he can make them disappear. With Hopper's permission, Manny takes the Queen on "stage" with him. In actual fact, the Queen has escaped under the wings of Dim. When Manny lifts the box and the grasshoppers see that the Queen has disappeared, they accept it as part of the magic act. Gypsy flaps her wings and bows with Manny as the crowd cheer her, but it is really a signal for Flik to fly down with the fake bird. Hopper soon grows irritable when Manny fails to bring the Queen back, and the grasshoppers close in on the circus bugs. However, they all look up in horror as the fake bird (unknown to them, driven by Flik) swarms over them.
The ants attack Hopper, and plunge him into the circus cannon. Just as they are ready to fire him as far away from Ant Island as possible, it begins to rain. The rain knocks over the cannon, and Hopper escapes. He then flies off with Flik. Francis, Slim, Tuck and Roll, Rosie, Dim and Heimlich take chase. Tuck and Roll manage to pull off one of Hopper's antennae, but the circus bugs soon get lodged in a group of branches. Princess Atta flies past, and snatches Flik away from Hopper. Flik and Princess Atta lead the grasshopper to the real bird's nest, where the ants hide. The real bird suddenly appears, but Hopper thinks it is another one of the ant's tricks. To his horror, the bird picks him up and drops him into a nest of three hungry chicks, thus ending Hopper's reign of terror and insult on the ant colony. The grasshoppers are defeated, and the ants have their island back.