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Extreme summer heat slows down mosquitos, leads to decline in repellent sales

(Mainichi)
An Asian tiger mosquito is seen in this photo provided by Earth Corp.

Even Japan's mosquitos can't catch a break during this year's record-breaking heat.

Experts say that mosquitoes lose their desire to suck blood when the temperature exceeds 35 degrees Celsius -- an event that has occurred quite often this scorching summer -- and this had led to fewer people feeling like they were bitten by the pests, as well as the sales of anti-mosquito products declining.

Still, the blood-sucking insects will be lurking even after September, and people should be aware of letting their guard down along with the falling temperatures.

"This summer I think I've only been bitten by a mosquito a few times," said 70-year-old Masakatsu Saito, a staff member at Fukuoka City Zoological Garden. Each year, the facility located in southern Japan has used mosquito repellent and coils to deal with the mosquitoes that swarm over the zoo, which is surrounded by trees and bodies of standing water. This summer, though, the decrease in the numbers of mosquito bites has become a hot topic among the zookeepers.

A study by the Institute of Pest Control Technology, based in Yachiyo, Chiba Prefecture, east of Tokyo, confirmed that the severe heat this year has an effect on the insects. Institute head Yoshikazu Shirai explained, "Mosquitoes lose their desire to suck blood at temperatures of 35 degrees or higher." In addition, bodies of water where mosquito larvae grow may have also dried up due to the blazing sun. "Presumably, there were fewer larvae that became fully grown adults," he said.

According to the Japan Meteorological Agency (JMA), during the 61 days from July 1 to Aug. 30, Kurume, Fukuoka Prefecture, in southern Japan, had 44 days with temperatures of 35 degrees or higher. Hita, Oita Prefecture, also in southern Japan, had 42 such days, Tajimi, Gifu Prefecture, in central Japan, recorded 38, and north of Tokyo, the Gunma Prefecture city of Tatebayashi and the Saitama Prefecture city of Kumagaya both had 32 days with temperatures of 35 degrees and over, according to the JMA data. Kumagaya set a record high for Japan at 41.1 degrees, while the suburban city of Ome set a record for Tokyo at 40.8 degrees.

Tokyo-based Earth Corp., which sells insect repellents and insecticides, suffered a roughly 5 percent drop in sales from January to July this year, compared to sales during the same period last year -- possibly because mosquito activity was slowed down by the heat. A spokesperson was surprised, since he had seen sales rise with the heat in the past. A representative from another manufacturer with decreased sales said, "One reason for the fall in sales may be due to a change in people's behavior, such as remaining indoors (because of the heat)."

Still, Earth Corp. warns that Asian tiger mosquitoes' desire to suck blood peaks at the end of September, when the bugs lay their eggs, since the insects cannot make it through the cold of the winter. These mosquitos may begin to actively bite people once temperatures have settled down to between 25 and 30 degrees.

The pest control institute is also cautioning people to "stay on guard and avoid wearing outfits that expose skin when visiting places where there may be many mosquitoes."

(Japanese original by Keisuke Muneoka and Shunsuke Yamashita, Kyushu News Department)

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