Venomous and aggressive fire ants from abroad have been found in seven prefectures since the first discovery in late May in Amagasaki, Hyogo Prefecture, in cargo inside a freight container that had come through Kobe port from China. Both the national and local governments should not spare any efforts in preventing the species from propagating in Japan.

The reddish brown ants with a blackish-red belly, which originate in South America, range from 2.5 to 6 mm in length. They are known for a sting that can cause anaphylaxis, a severe allergic reaction, including breathing problems. A queen fire ant can lay some 2,000 eggs a day. There are no signs yet that fire ants have propagated in Japan. Once they do so, however, they could potentially cause damage to agriculture and animals, and affect people’s lives.

As cross-border movements of people and goods increase in the age of globalization, the possibility is rising of harmful species invading Japan. Government authorities need to carry out thorough quarantine steps, including measures designed to prevent fire ants from making nests. A total of 68 ports in this country are destinations of regular freight container shipments from China and Taiwan, where fire ants are now widespread.

In Japan, the temperature and amount of rainfall in areas up to southern Tohoku offer good conditions for the propagation of the species. The Environment Ministry has been on the alert for its invasion since it designated fire ants in 2005 as an invasive species that can destroy ecosystems.

In the 1930s, fire ants from South America entered the United States and became widespread in the country’s southeastern regions. It is thought that the ants arrived in shipments of sand and earth used as ballast in ships. By the 1980s, they spread to the West Coast. Since fire ants do not have a natural enemy in the U.S., the presence of abundant plants on which they feed has contributed to their explosive increase there. In the U.S., the damage from fire ants is not limited to domestic animals and agricultural products like soybeans, potatoes and citrus fruits, which disrupts the ecosystems. Electricity facilities and cables have also fallen prey to the ants. One estimate puts economic losses caused by fire ants in the U.S. at an equivalent of ¥600 billion a year.

After the turn of the century, the presence of the venomous ants was confirmed in Australia, Taiwan and China. Studies of their genes show that the ants were transported from the U.S. In short, many of Japan’s major trading partners have become infested with fire ants. In that sense, the introduction of the species here was inevitable.

Measures that national and local governments have so far taken include inspections in and around sites where fire ants have been found and placing bait containing insecticides at ports handling marine traffic from countries where the species exists in large numbers. The central government should also work with other governments to ensure that strict pest control of Japan-bound cargo will be carried out.

Ants, which have symbiotic relations with many other creatures, play an important role in sustaining natural ecosystems. The spread of fire ants can pose a threat to native ants. Authorities should ensure that the wide use of insecticides in the fight against fire ants does not eradicate local species.

Since fire ants can propagate in broad areas of the world, including Asia, Africa and Europe, the study of effective ways to prevent their spread will be indispensable. Global warming may further expand the areas where they can propagate. The central government should support such studies to help enhance the international community’s fight against the species.

Unlike ants that are native to Japan, fire ants build dome-like anthills 15 to 50 cm in height and 25 to 60 cm in diameter. Their nests are constructed in places with sufficient sunshine to ensure a certain amount of warmth for reproduction. Parks, farmland and roadsides are suitable habits. People who find their nests should waste no time in reporting their locations to local governments or regional offices of the Environment Ministry. The inner structures of their nests are so complicated that pouring hot water on them will not kill the fire ants that live deep inside. People who are stung by fire ants should seek immediate medical treatment.

The government should fully inform port and airport workers and people in general about fire ants through means including distribution of flyers, and encourage them to quickly report any suspected sightings. The cooperation of the public will be crucial to mounting a successful defense against this invasion.

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