But by July, most of them are gone.

Where do they go?

To find the answer, Li Xinde, a student from National Taiwan University, marked four thousand butterflies in June 2000 to track them.

Later in July, one of them was caught by a man in Japan.

He noticed the butterfly was marked with numbers and letters.

After taking a picture of the butterfly and posting it on the Net, the man was told that the butterfly came from Taiwan.

The news surprised a lot of people because very few knew that butterflies could fly across the ocean like some wild geese.

More exciting news came after Li's study.

In November 2001, a chestnut tiger butterfly with the mark "SOA118" was collected in Pingtung.

The butterfly was marked and released from Osaka, Japan.

It flew almost 2,300 kilometers from Japan to Taiwan.

Many scientists were excited about the news because it showed that chestnut tiger butterflies also fly from Japan to Taiwan.

How far can chestnut tiger butterflies travel?

Why do they fly across the ocean?

Today, scientists are still studying them to find out the answers to these questions and more.