21、Monarch Butterfly (金斑蝶) Profile

       Monarch butterflies are known for the unbelievable mass movement that brings millions of them to California and Mexico each winter. North American monarchs are the only butterflies that make such a massive journey-up to 3,000 miles (4,828 kilometers). The butterflies must begin this journey each fall ahead of cold weather, which will kill them if they delay too long.

       Monarch butterflies begin life as eggs and hatch as little worms that eat their eggshells and finally, eat the milky plants on which they were placed. When fat worms become juicy, colorful and hairy, they create a hard protective case around themselves as they enter the cocoon stage. They come out as beautifully colored, black-orange-and-white adults. The colorful pattern makes monarchs easy to identify, and the unique pattern warns their enemies that the insects are terribly tasting and poisonous.

       Butterflies that come out from cocoon in late summer and early fall are different from those that do so during the longer days and warmer weather of summer. These monarchs are born to fly, and know that they must prepare for their long journey because of the changing Weather. However, only monarchs born in late summer or early fall make the move, and they make only one found trip. By the time next year's winter moving begins, several summer generations wilt have stayed and died. It will be last year's settlers' great grand children that make the trip. Yet somehow these new generations know the way, and follow the same routes their ancestors took-sometimes even returning to the same tree.

       Many scientists are concerned about the eastern population of monarchs, which spend the summer east of the Rocky Mountains. This group is occurring in ever smaller numbers, and its survival now is threatened by a series of natural disasters in the Mexican winter grounds and by reduced milkweed plants in their summer home.

1．What will happen to the monarch butterflies if they don't leave in fall?

      A．They can't survive the very low temperature, in winter

      B．They can't keep their pattern colour in changeable weather

      C．They will be blown down by the strong wind in winter

      D．They will be separated from each other by the cold weather

2．Form the passage we can learn that Monarchs ____________.

      A．feed on their own eggs instead of milky plants

      B．experience three life stages before they can fly

      C．a(chǎn)re difficult to be picked out from other insects

      D．a(chǎn)re very delicious, though they are poisonous

3．Which of the following about Monarchs is TRUE?

      A．Monarchs seem to know their ancestor's hometown

      B．Only last year's settlers' grandchildren make the trip

      C．All the summer generations will have stayed and died

      D．Only monarchs born in early autumn make the move

4．The writer seems             about the present survival situation of Monarchs.

      A．confident            B．worried        C．disappointed       D．hopeful