Crazy ant is any of a group of ants known for their irregular movements, especially when disturbed. They can be found almost everywhere, except Antarctica. Crazy ants measure up to 1/5 inch (5 millimeters) long. They have long legs and long antennae (feelers). The crazy ant produces a harmful acid that it can spray to defend against predators (hunting animals) and to overcome prey.
One kind of crazy ant is the yellow crazy ant. It is considered a pest across its range. Scientists do not yet know where this ant originated. But it has spread to such places as Northern Australia, South and Southeast Asia, East Africa, Mexico, and many islands in the Indian Ocean and Pacific Ocean. On these islands, yellow crazy ants have caused much damage to the natural environment.
Yellow crazy ants are especially known for the damage they have caused on Christmas Island. Christmas Island is in the Indian Ocean, about 1,645 miles (2,650 kilometers) northwest of Perth, Australia. The island is famous for its yearly migration of red crabs. Swarms of crazy ants have been killing off the red crabs. Normally, these crabs eat dead leaves and seeds on the forest floor. With the loss of so many crabs, many seeds are not getting eaten, and so plants can grow that normally would not. This effect has completely disrupted forest ecosystems on the island. Yellow crazy ants also provide protection for scale insects. Scale insects produce nutritious honeydew, a liquid made by drinking the sap of trees. The yellow crazy ant eats the honeydew. Scale insects protected by ants are killing trees. The loss of trees enables more sunlight to reach the forest floor and alters which animals can live on Christmas Island. Some birds, for example, can no longer find a suitable place to nest there. Crazy ants can also drive adult birds from their nests and kill and eat their hatchlings.
People have had some success controlling the crazy ant population by using a type of poison. The ants eat the poison and distribute it through the colony, wiping out the colony. Poisoning cannot kill all the ants in a region, however, so wildlife managers are carefully monitoring crazy ant populations. Biologists are also introducing a parasitic wasp to Christmas Island. The wasp preys on the scale insects that produce the main food for crazy ants. The biologists hope to control the population of crazy ants by reducing the supply of their preferred food.
