Taiwan News, Staff Writer , Central News Agency
2009-03-21 05:26 PM

The National Expressway Bureau sets up protective nets on National Freeway No. 3 near the Linnei section in Yunlin County on March 20 to protect purple milkweed butterflies' safety during migration northward in spring.

The death rate of purple milkweed butterflies during their annual migration has dropped substantially since highway authorities adopted protective measures on one of the country's two main freeways around Tomb-Sweeping Day in 2007, an official said Friday.

The National Expressway Bureau (NEB) under the Ministry of Transportation and Communications has consistently taken a number of measures between late March and early April to protect the milkweed butterflies' safety over the past couple of years.

The time period is when the colorful insects pass over a section of National Freeway No. 3 to reach their breeding ground in northern Taiwan after wintering in the south.

In addition to using protective nets and ultra-violet light to aid the migrating butterflies, the bureau has even closed one northward lane of the freeway at some points and restricted the speed of vehicles to avoid hitting the insects.

According to the results of a field survey by professor Yang Ping-shih (楊平世) from National Taiwan University, the ratio of the butterflies killed while flying over the freeway declined from 3 percent in 2007 to 0.3 percent in 2008.

Last year, Yang led a team to observe the migration of purple milkweed butterflies at Linnei in Yunlin County from March 1 through May 31.

Yang told a news conference Friday that the peak period of butterfly migration fell between March 22 and April 7 and that the largest number appeared on April 5 when more than 1,000 insects flew over the highway per minute.

Speaking on the same occasion, NEB Director Lee Tai-ming (李泰明) said the protective measures will be expanded this year, with one northbound lane near the Linnei section of the expressway to be closed for 3 kilometers, up from 2 kilometers a year earlier, and the number of protective nets to be expanded from 460 meters to 660 meters.

[Read the original story at http://www.etaiwannews.com/etn/news_content.php?id=899063&lang=eng_news