Yellow crazy ant facts for kids
Quick facts for kids Anoplolepis gracilipes |
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| Scientific classification | |
| Genus: |
Anoplolepis
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gracilipes
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| Synonyms | |
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Formica longipes, |
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The yellow crazy ant (Anoplolepis gracilipes) is a type of ant. It originally came from Southeast Asia. People have accidentally moved it to many warm, tropical places around the world.
It's called "crazy" because it moves in a very wild and jerky way when something disturbs it. Its long legs and antennae make it one of the biggest invasive ant species on Earth.
Like other invasive ants, such as the red imported fire ant or the Argentine ant, the yellow crazy ant is a "tramp ant." This means it can easily settle and take over new places. It does this because it's aggressive towards other ant species, but friendly to its own kind. It's also good at finding food and has very large colonies. It's also known as the long-legged ant or Maldive ant. The International Union for the Conservation of Nature (IUCN) has listed it as one of the "one hundred of the world's worst invasive species." It has spread to places like Hawaii and Seychelles. It has even formed huge supercolonies on Christmas Island in the Indian Ocean.
Contents
What They Look Like
The Anoplolepis gracilipes is a fairly large ant. It is yellow to orange in color and has long legs, big eyes, and very long antennae.
Even though A. gracilipes is the only invasive ant in its group (genus Anoplolepis), it can look like other ants. For example, Leptomyrmex and Oecophylla ants are similar in size and have long limbs. You can tell Anoplolepis apart from Leptomyrmex because it has a special opening called an acidopore. You can tell it apart from Oecophylla by its more compact waist part, called a petiole. These other ant types are not invasive.
Some invasive ants like Camponotus and Paratrechina can also look similar to A. gracilipes. Also, some Pheidole ants can be thin with long legs and antennae. However, you can tell them apart from A. gracilipes because they have a two-part waist.
A. gracilipes is found all over tropical areas, especially in the Pacific. It is most famous for causing a big environmental problem on Christmas Island. Because it can harm local plants and animals, people try hard to stop it from spreading to new places.
Where They Live and How They Spread
The yellow crazy ant naturally lives in the warm, wet lowlands of Southeast Asia. It also lives on islands nearby in the Indian and Pacific Oceans.
It has been brought to many tropical and subtropical places. These include northern Australia, some Caribbean islands, and islands in the Indian Ocean like Seychelles and Christmas Island. It's also found on Pacific islands such as Hawaii and the Galapagos archipelago.
These ants can live in farms that grow cinnamon, citrus fruits, coffee, and coconuts. Because they can build nests almost anywhere, they often spread by traveling on trucks, boats, and other human transport.
Crazy ant colonies usually spread by "budding." This means that new queens and workers leave their old nest to start a new one nearby. They rarely fly to new places. Colonies that spread by "budding" usually move slowly. They need humans to help them reach far-off areas. In Seychelles, A. gracilipes has been seen moving about 400 meters (about 1,300 feet) in a year. But on Christmas Island, they spread faster, about 3 meters (10 feet) a day, which is about one kilometer (0.6 miles) a year.
What They Eat
A. gracilipes is known as a "scavenging predator." This means it eats many different kinds of food, which is common for invasive species. It eats grains, seeds, insects, and dead things, even dead animals. They have been seen attacking and taking apart small creatures like isopods, myriapods, molluscs, arachnids, land crabs, earthworms, and other insects.
Like all ants, A. gracilipes needs food rich in protein for the queen to lay eggs. Workers need carbohydrates for energy. They get carbohydrates from plant nectar and a sugary liquid called honeydew. Honeydew is made by insects like scale insects and aphids. Studies show that crazy ants rely so much on scale insects that if there aren't enough, the ant population won't grow as much.
Working Together (Mutualism)
Crazy ants get a lot of their food from scale insects. Scale insects are plant pests that suck sap from trees and release honeydew. Ants eat this honeydew. In return, the ants protect the scale insects from their enemies and help them spread to other trees. This is an example of mutualism, where two different species help each other. The honeydew that the ants don't eat drips onto the trees. This causes a black, moldy growth called sooty mold on the leaves and stems. This makes the plants look bad and can make them less healthy.
The ants protect the scale insects by "nannying" their young, mobile stages and keeping away their natural enemies. Experiments have shown how strong this connection is. In places where A. gracilipes ants were removed, the number of scale insects dropped by 67% in 11 weeks. After 12 months, there were no scale insects left.
In Australia
In Australia, yellow crazy ants have been found in over 30 places in Queensland. They are also in Arnhem Land in the Northern Territory, where there is a large, spread-out group of them. A single group was found and removed in New South Wales. In Western Australia, yellow crazy ants have been found in shipping containers arriving at Fremantle.
The main problem area in Queensland is about 830 hectares (about 2,050 acres) in and around the Wet Tropics of Queensland rainforest, which is a World Heritage Site. The ants in the Northern Territory cover about 2,500 square kilometers (about 965 square miles). This area is larger than the Australian Capital Territory.
Scientists believe that yellow crazy ants could spread across northern Australia, from Queensland to Western Australia. They could also spread into many parts of Queensland and coastal New South Wales. Areas with the best habitat and weather, like the Wet Tropics rainforests, will likely be hit the hardest.
The Queensland government studied the costs and benefits of dealing with the ants. They found that yellow crazy ants could cost Australia's economy over $3 billion (AUD) if they are not treated. This study did not even include the possible harm to Australia's wildlife. What happened in tropical rainforests overseas, especially on small islands like Christmas Island, can help us understand these impacts.
Impact on Christmas Island
Crazy ants have had a huge impact on the plants and animals of Christmas Island.
The crazy ant causes a lot of damage to the island's ecosystem. They kill and push out crabs on the forest floor. The super-colonies also greatly reduce the number of crabs moving to the coast. This has led to a fast drop in land crab numbers – killing up to 20 million of them. Land crabs are very important to Christmas Island's environment. They are a keystone species, meaning they are vital to the forest. They dig burrows, turn over the soil, and fertilize it with their droppings.
Young plants that crabs used to eat now grow freely, changing how the forest looks. Weeds also spread into the rainforest because there are no crabs to control them. One big change is the increase in stinging trees (Dendrocnide peltata). These now grow in many places where people often go. The forest canopy also changed because the scale insects, protected by yellow crazy ants, multiplied and killed old trees.
Robber crabs, red crabs, and blue crabs are completely wiped out in areas where the ants have taken over. Other animals that live on the ground and in trees, like reptiles and other small creatures in the leaf litter, have also decreased. During crab migrations, many crabs move through ant-infested areas and are killed. Studies show that the ants have taken over the burrows of about 15–20 million crabs. They kill and eat the crabs and use their burrows as nests. This has greatly reduced the number of red crabs and made their yearly land migrations much more dangerous.
Even though crazy ants don't bite or sting, they spray formic acid to defend themselves and to catch their prey. In areas with many ants, if a land crab moves, it disturbs the ants. The ants then spray formic acid as a defense. The high levels of formic acid on the ground eventually hurt the crabs. They usually become blind and then die from dehydration (as they try to wash off the acid) and exhaustion. As the dead crabs decay, the ants eat the protein.
Crazy ants kill animals but help scale insects. More scale insects lead to trees dying, even large forest trees. These changes cause a chain reaction of bad effects, like more weeds, which greatly changes the forest.
Giant Ant Cities (Supercolonies)
Christmas Island is a main focus for international efforts to control these ants. These supercolonies spread further and cause more damage than single colonies. They are the biggest known threat to the island's wildlife.
Staff from Christmas Island National Park have been working to control ant numbers. With help from experts and the Australian Government, they are managing to hold them back.
Another supercolony almost destroyed the birds on Johnston Atoll in the Pacific Ocean. This huge colony covered almost a quarter of the island. It had up to 1,000 queens in an area just 6 meters (about 20 feet) wide. People believe this ant problem has now been removed.
How People Are Fighting Them (Control Measures)
To reduce the harm crazy ants cause to red crabs and Christmas Island's ecosystems, Parks Australia started a big aerial baiting program in 2009. This followed an earlier one in 2002. The first step was to survey the whole island to find the exact locations of the supercolonies. For several months, staff walked across the island, checking over 900 spots. This created a map showing where the crazy ant supercolonies were, how many red crab burrows there were, and other wildlife information.
In September 2009, a helicopter was used to carefully spread bait over the crazy ant supercolonies. These covered 784 hectares (about 1,937 acres) of the island. A very weak bait (0.1% fipronil) was used to control the ants. Monthly checks of these baited areas showed that crazy ant numbers dropped by 99%.
Park staff worked hard to make sure the bait didn't harm other animals. They dropped food from the helicopter to attract robber crabs away from areas that were about to be baited. This method, along with the weak fipronil bait, worked very well. Very few robber crabs were harmed, and no red crabs were known to be killed by the baiting.
While baiting has slowed the decline of the red crab, its effects on the crazy ant populations are only temporary. Escaping colonies can invade the treated areas again. Also, it is expensive and needs a lot of people to do the work. To find a better solution, Australian Parks imported a small (2 mm) wasp called Tachardiaephagus somervillei in December 2016, after research. They started breeding these wasps for release. This wasp only attacks scale insects. It is a strong predator of the yellow lac scale insect, which is believed to be one of the biggest sources of honeydew for crazy ants on Christmas Island.
Researchers from La Trobe University in Melbourne, funded by Parks Australia, began looking for natural ways to control the ants in 2009. While the ants eat many things, studies have shown that honeydew is a very important part of the diet for Christmas Island crazy ants. Samples from ant colonies that are growing fast have more honeydew in their diet than when the colonies are shrinking. Also, when ants couldn't get to honeydew (by wrapping trees where scale insects feed), the colony greatly decreased. Ant activity on the ground fell by 95% in just four weeks. In the lab, colonies with little sugar were compared to those with lots of sugar. Those with lots of sugar had more fertile queens and fewer worker deaths. The workers were also more aggressive towards other ant species and explored more. This shows why the ants decline when they can't get to scale insects in the wild. It confirms that less honeydew will greatly reduce the ants' ability to form supercolonies.
While controlling the yellow lac scale insect is expected to control the yellow crazy ant on Christmas Island, it might not help on mainland Australia. There are at least a dozen other honeydew-producing insects there, as well as nectar from native acacia trees. All of these provide food for yellow crazy ants.
Experts continue to ask for a well-funded, long-term baiting program on mainland Australia.
Images for kids
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Yellow crazy ant on a leaf.
See also
In Spanish: Hormiga loca para niños
