May 18, 2018

In Southeast Asia, a newly identified ant species has a unique defense mechanism: it explodes! When threatened, or when in the grips of an enemy insect, the new tree-dwelling ant species Colobopsis explodens bursts toxic yellow goo from its abdomen, killing or chasing off its attacker. The ant dies in the effort, but it is an effective way of defending the colony.

A worker Colobopsis explodens ant strikes a formidable defensive pose. Credit: © Alexey Kopchinskiy, Pensoft Publishers

The self-sacrifice of the Colobopsis explodens ant may sound drastic, but it is not uncommon in the insect world. Many bees die after stinging an attacker, and certain aphids, termites, and other ants also practice autothysis—the act of self-sacrifice through explosion.

Ant colonies differ enormously in size. A colony may have a dozen, hundreds, thousands, or in rare cases, even millions of members. A colony usually has one or more queens. Ant queens are females whose chief job is to lay eggs. An ant colony also includes the ant young or larvae. Male ants, who have wings, live in the colony only at certain times of the year. Their only job is to mate with young queens, who also have wings. The rest of the colony consists mostly of workers. These wingless female ants do not lay fertile eggs but instead build the nest, search for food, care for the queen and the young, and protect the colony. Unlike queens, workers commonly leave the nest and can often be seen walking about on the ground or in trees.

The small, reddish-brown Colobopsis explodens workers are the ones who give themselves up for the good of the colony. During combat, the worker ant bites down on the enemy, lifts its lower body, and contracts its muscles so hard that its skin splits open, releasing sticky, toxic fluid from its abdomen. The explosion kills the ant, but the curry-smelling goo either kills or repels the enemy. If invading insects make it past the exploding ants’ front line, the colony has a unique second line of defense—worker ants with enlarged, plug-shaped heads. These ants gather together to barricade the nest’s entrance, keeping enemies out.

Exploding ants have been known for quite some time, but Colobopsis explodens is the first new species to be discovered since the 1930’s. Scientists do not know much about exploding ants, but this new species provides the opportunity to learn more.

June 27, 2016

Everyone knows how annoying ants can be, particularly when they invade our homes or picnics. Imagine, however, relentless swarms of ants so destructive that they ravage ecosystems, destroy electrical equipment, and even threaten to drive people from their homes. This is the reality facing those on the front lines of the crazy ant invasion.

Crazy ant
Credit: © Brberrys, Shutterstock

Crazy ant is the name for a group of ants known for their irregular movements, especially when disturbed. They can be found all over the world except Antarctica. Most crazy ants measure about 1/5 inch (5 millimeters) long. They have long legs and long antennae (feelers). Crazy ants spray a harmful acid to attack their prey. They are mostly carnivorous, but many species have a mutually beneficial relationship with certain types of insects that feed on plants. Crazy ants protect these insects from predators. The insects in turn provide the ants with a nourishing fluid called honeydew.

In recent years, different kinds of crazy ants have spread throughout the globe, disrupting habitats wherever they go. Most of these invasions were likely started when humans accidentally transported the ants to new locations. Global warming has probably accelerated the invasions as well.

Yellow crazy ants (Anoplolepis gracilipes) have invaded Christmas Island, about 1,000 miles (1,600 kilometers) northwest of Australia, where they have decimated the island’s famous red land crabs. Swarms of ants attack crabs by spraying acid into their eyes and in the joints of their armor. The red crabs have to use up water to flush out the acid, and die of dehydration if they can’t get to a water source quickly. With fewer red crabs to eat seeds found on the floor of the rain forest, the makeup of the plant population has completely changed.

In the southern United States, the tawny or Rasberry crazy ant (Nylanderia fulva) has come into conflict with people. In some places, tawny crazy ants are pushing out fire ants, which are themselves an invasive species to the area. In conflicts between the two, tawny crazy ants spray themselves with their own acid, which neutralizes the fire ant’s toxic venom.

Tawny crazy ants can be serious pests to humans. For reasons that are not yet known, the ants often attack electrical equipment. Millions of ants pour into air conditioners, computers, or electrical outlets, where they are electrocuted. Eventually, their bodies form links between wires, damaging or destroying the device. They reproduce so quickly that they are almost impossible to remove once established. Exterminators might wipe out billions of crazy ants on a single property, so many that brooms and trash bags are needed to remove the bodies, only for them to return in greater numbers the following year.

Programs to control crazy ants have met with little success. At best, pesticides are only temporarily effective. Australian officials plan to introduce a wasp to Christmas Island to kill the honeydew-producing insects on which yellow crazy ants rely. Unless these efforts and others like it succeed, people may have to adjust to life with crazy ants.