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Midge population growing, study finds

Forget about cockroaches and ants -- there's a new bug in town.

Called the "little black mosquito" in Chinese, this minute pest, a kind of midge, has spread countrywide and poses a new threat to human health.

The results of a long-term research project by National Chung Hsing University's department of entomology found that the midges, Forcipomiya taiwana, are present in all parts of the country, with the exception of Pingtung and Taitung counties.

Associate professor Tu Wu-chun (杜武俊) said that in a 1994 study, the bugs were not recorded in Taipei, Miaoli, Kaohsiung, Pingtung and Taitung counties and cities and Keelung.

In 2006, the bugs were recorded in all cities and counties except Taitung and Pingtung and the density of the bug population had increased sharply, Tu said.

Furthermore, while the bugs used to be found only at lower altitudes, they are now found in mountainous regions.

In the past, the midges were mainly active from late March through their peak season of May to August. But in recent years, the bugs have been found active in some areas year round.

Temperature is an important factor that limits the activity of the bugs.

When a series of cold fronts hit the country during the Lunar New Year and temperatures dipped below 15oC, Tu's research team found no midges in Dakeng (大坑), Taichung. But once the temperature rose to 22oC, the team caught more than 800 of the bugs.

The team also found that females will not lay eggs when temperatures are above 35oC.

Tu said that global warming, human settlement and cars may be behind the spread of the bugs.

Adult Forcipomiya taiwana feed on blood during the day and are at their most active between 12pm and 3pm.

In a paper on the species published earlier this year, Tu and his colleagues Hsieh Poh-yueh (謝伯岳), Tang Li-cheng (唐立正) and Shih Chang-liang (施昌良) said that the midges could affect students' learning, lower the quality of life and have a negative impact on tourism.

Solving the bug issue, the researchers said, should be a high priority for schools, communities, the tourism industry and the central government.

The study found that the bug population was most dense in Dakeng, where more than 1,000 bugs were recorded in a single survey.

Areas close to Bagua Mountain (八卦山) in Huatan Township (花壇), Changhua County, came in second with a 700 to 800 count. Between 500 and 700 specimens were counted in Lugu Township (鹿谷), Nantou County.

The presence of the "little black mosquitoes" has become an annoyance for visitors at major tourist attractions in Nantou and Yunlin counties, the team said.

The bugs have also halted a plan by the Taichung City Government to invest in tourist facilities at Dakeng.

The team said that any location where more than 100 of the bugs can be counted in a single survey should be seen as critical.

The main method to fight the midges is by spraying insecticides, but Tu said that spraying chemicals could only bring limited success and was only a short-term solution to the problem.

Tu said households could contribute to the fight against the midges by taking out the trash every day. People should also keep ditches, balconies, window boxes, flowerpots and shrubs clean and dry to help reduce the population of midges.
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