英語時差：螢火蟲數(shù)量減少，專家憂心忡忡

Preecha Jiabyu used to take tourists on a rowboat to see the banks of the Mae Klong River aglow with thousands of fireflies.

These days, all he sees are the fluorescent lights of hotels, restaurants and highway overpasses.

"The firefly populations have dropped 70 percent in the past three years," said Preecha, 58, a former teacher who started providing dozens of rowboats to compete with polluting motorboats.

The fate of the fireflies drew more than 100 entomologists and biologists to Thailand's northern city of Chiang Mai for an international symposium on the "Diversity and Conservation of Fireflies."No single factor is blamed, but researchers in the United States and Europe mostly cite urban sprawl and industrial pollution that destroy insect habitat. The spread of artificial lights also could be a culprit, disrupting the intricate mating behavior that depends on a male winning over a female with its flashing backside.

Republican presidential candidate John McCain stunned the U.S. political establishment and bolstered his image as a maverick by choosing the little-known female governor of Alaska as his running mate in the race against Democrat Barack Obama.

McCain's choice of Sarah Palin also means that no matter who wins in November, U.S. history will be made: Either the first black man will become president or the first woman will be vice president.

Palin offers risks and rewards for McCain. The choice of a 44-year-old, first-term governor to be his vice president could undermine one of McCain's main campaign themes: that Obama, a 47-year-old first-term senator, is too inexperienced to become president.

But Palin, whose nomination was announced on Aug. 29, could help McCain rally social conservatives, a core Republican constituency that has had an uneasy relationship with McCain. Palin has a strong anti-abortion record and opposes gay marriage.