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Deadly Fire Ants Invade Japan, Brought In via Trade Vessels From China

Juichiro Ito




South American fire ants, dubbed “killer ants” for their particularly potent venom, have been discovered in Japan. After being spotted in Hyogo Prefecture in May, they were subsequently found in Aichi Prefecture as well, and their invasion is expected to grow.


Many poisonous invasive species have come into Japan, and the Ministry of the Environment is advising caution.


“When they bite you, the pain is like being lit on fire, true to the name fire ant,” Dr. Takahiro Murakami, an expert in ant ecology at Kyushu University, described the feeling of having been bitten at a talk in Taiwan in 2010.


“It may induce a slight anaphylactic shock, dizziness, or palpitations. Your pupils contract, and your field of vision grows narrow,” he continued.


The fire ant, a reddish-brown ant roughly two and a half millimeters in length, is a species that does not stand out, but it is highly aggressive. When the dome-shaped anthills which it forms in open fields are destroyed, it unleashes its venom from a stinger found underneath its belly.


In the process of investigating one of these anthills, Murakami was attacked by hundreds of these ants crawling up his legs. They infiltrated a space between his gloves and clothing and stung him.


The active ingredient in the poison is an alkaloid chemical that destroys cells and produces pimple-like welts around the wound. The pain can last for up to two weeks.


It contains proteins that imitate allergy-inducing bee venom. The allergy reaction is extremely fast, inducing anaphylactic shock that can result in death. In the United States, over 100 people die of fire ant stings every year.


Fire ants originally used their venom to hunt. The ants can also eat vegetables, but when they form groups they can attack and hunt both small insects and small animals, such as earthworms and frogs. Their venom is a weapon necessary for their life.


However, this is extremely dangerous to humans, and the Ministry of the Environment advises people who discover fire ants to stay away from them and contact the ministry or related environmental authorities.


If you are stung, you should rest for 20 to 30 minutes. If symptoms worsen, the ministry advises visiting a hospital for diagnosis.



They Came From South America

Until 1942, fire ants were found only in the central part of South America. But according to Koichi Goka of the National Institute for Environmental Studies, “They have currently been discovered in over 15 countries and regions across the Pacific Ocean, including Japan.”


At first, they mainly invaded North America and the Caribbean islands, but entering the 21st century, within 5 years, they have quickly spread to Malaysia, Australia, Taiwan, New Zealand, and China.


This takes place amid the economic development of South and Central America. Large amounts of agricultural produce and natural resources are being exported to developing China and Southeast Asia, and fire ants come along with the freighters. Their arrival in Japan was only a matter of time.


The ants’ reproductive power and wide inhabitable region have spurred this invasion. A regular ant species has only one queen per colony, but fire ants have dozens of queens. Queen ants produce thousands of eggs every day, and, in a large nest, colonies can have over 10 million members. Anthills can stretch up to 10 meters underground, and removal is difficult.


Rapid Extermination is Key

On May 26, fire ants were discovered for the first time in Japan, inside a container on a shipping vessel arriving from China in Amagasaki City, Hyogo Prefecture. On June 16, it was discovered that the ants had formed a colony in an area where the container was temporarily stored.



Both of these colonies have been exterminated, but the Ministry of Land, Infrastructure and Transport, in response, has issued an urgent request for investigation to local authorities. On June 27, ants were again discovered on the outside of a container shipped from China.


Many poisonous invasive species have escaped extermination and settled on the Japanese islands. The tropical fire ant, which contains the same kind of poison as the South American fire ant, stowed away in goods shipped for the US army, and is currently present in Okinawa Prefecture and on the island of Iwo Jima in the Ogasawara Islands (Tokyo).


In June, it was newly discovered at Kobe port, and has been confirmed as present on mainland Honshu.


The red-backed spider, which has its home in temperate Australia, first appeared in Japan in 1995, and is currently present in over 40 prefectures from Okinawa to Hokkaido. The Asian hornet, native to China, arrived in Kyushu in 2012. The fire ant is not an exception.


Scorpions with lethal toxins, the giant Sydney funnel-web spider which has induced poison, or the little fire ant, a relative of the South American fire ant, may also possibly invade in the future. The Ministry of the Environment has recommended a strengthening of countermeasures at ports.


However, the arrival of invasive species will continue as long as there is trade. According to Goka, “We cannot avoid their entering the country. To the best of our ability, we must exterminate them on discovery so that they don’t settle here.”


Juichiro Ito is a staff writer of the Sankei Shimbun Science news department.



(Click here to read the original article in Japanese.)



Juichiro Ito is a staff writer of the Sankei Shimbun Science Department at Tokyo HQ office.

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