As the nation enters the autumn tourist season, concerns are growing over hornets, whose nests and number of workers are larger than usual this year because of the warmer spring and limited rain during the rainy season.
Hornet stings have been reported in Gifu and Nagano prefectures since August. Experts warn that worker hornets tend to become more aggressive when there are more of them, and in autumn when they need to protect the larvae that will become their new queens.
Hornet stings can cause anaphylaxis, including shortness of breath and vomiting, and at times can be life-threatening. Twenty-three people died due to bee stings in 2015, 19 in 2016 and 13 in 2017, according to the health ministry’s demographic statistics.
Experts say someone stung by a hornet should wash the wound with cold water and seek medical attention. Someone who feels dizzy, whose body starts itching, or those stung on the head or neck, or multiple times, are urged to call an ambulance right away.
In late September, yellow tape warning people to keep out were placed around trees at three locations in Nagoya’s Meijo Park, which surrounds Nagoya Castle, with signs urging visitors to watch out for hornets.
Kumiko Hattori, 47, who was walking through the park to take her daughter to a swimming school, said: “We avoid walking near the signs because my child is scared of hornets.”
“We placed the tape to prevent bee attacks after receiving reports from visitors that they saw large bees,” said an official who manages the park. “We confirmed a couple of what appear to be hornets near tree sap.”
According to Mai Mitsubayashi, an official in charge of pest inspections with the Nagoya Municipal Government, 1,714 hornets were captured in August using traps installed at 10 parks in the city — roughly 30 percent more than the average of 1,276 during the month over the past decade.
Numbers of black-tailed hornets — the type commonly seen in residential areas — have increased to nearly five times more than in an average year, Mitsubayashi said. “They are not so aggressive, but they can attack people,” she said.
To avoid angering hornets, Mitsubayashi advises people not to wear black clothes or wear perfume when they go into the woods or go near their nests. Japanese giant hornets sometimes build their nests underground, so people might be disturbing them without knowing it, she said.
Suzumebachi 110-ban (which roughly translates as “emergency hornet handlers”), a company in Minamiise, Mie Prefecture, that removes hornet nests in the Tokai region, said the number of requests to remove nests of aggressive Japanese yellow hornets has nearly doubled between June and August compared with an average year.
Hidehisa Nishi, who heads the firm, said the size of nests is also larger this year. “Usually the nests are about the size of a dodgeball, but this year there are more nests about the size that fits in the arms of an adult,” Nishi said.
Experts attribute the increase in hornets and the larger nest size to the change of climate this year.
According to Masato Ono, a professor of applied entomology at Tamagawa University who has written a book about hornets, the temperature during early spring was higher this year, making queen hornets come out of hibernation and start building nests earlier.
The amount of rain that prevents nest-building during the rainy season was also less than usual, resulting in bigger nests, he said, adding that bigger nests mean there are more of the worker hornets that become more aggressive in autumn when they have to protect larvae.
Ono said hornets show alarm, such as buzzing around, before going into attack mode, and advised people to slowly back away because sideways movements can irritate hornets.
If people find nests, they should ask experts to remove them, Ono said, adding that the best time to remove the nests is during the night.
This section features topics and issues from the Chubu region covered by the Chunichi Shimbun. The original article was published Oct. 7.