21. What does the speaker say about monarch butterflies reproduction?

21。关于帝王蝶的繁殖，讲话人提到了什么？

20. Where do monarch butterflies settle at the end of the migration?

20。帝王蝶在迁徙的最后会安顿在哪里？

Scientists learn about monarch butterflies migration by capturing and placing identifying tags on the insects.

科学家是通过捕捉帝王蝶并在它们身上贴上识别标签来研究它们的迁徙的。

The United States has not listed monarch butterflies under the Endangered Species Act.

美国尚未将黑脉金斑蝶列入《濒危物种法案》。

For example, monarch butterfly caterpillars can fit on a pencil eraser when they hatch.

例如，帝王蝶毛虫孵化时可以放在铅笔橡皮擦上。

Homero Gomez managed a sanctuary for monarch butterflies which migrate from Canada and the US every winter.

奥梅罗·戈麦斯为每年冬天从加拿大和美国迁徙过来的黑脉金斑蝶建立了一个避难所。

Spectacular examples include the long-distance migrations of monarch butterflies and salmon.

壮观的例子包括帝王蝶和鲑鱼的长距离迁徙。

A single monarch butterfly stepped out, looked around, and flitted away.

一只帝王蝶走了出来，环顾四周，然后飞走了。

The most famous of these has got to be the monarch butterfly.

其中最著名的当属帝王蝶。

Well, a couple months ago, we found four monarch butterfly caterpillars in our backyard.

凡妮莎：嗯，几个月前，我们在后院发现了四只帝王蝶毛虫。

IUCN estimates that the population of monarch butterflies in North America has fallen between 22 percent and 72 percent over 10 years, depending on the measurement method.

国际自然保护联盟，北美黑脉金斑蝶的数量在过去10年里下降了22%到72%，具体数值取决于测量方法。

They included Samuel Scudder, who named the monarch butterfly and wrote a magisterial, three-volume work about North American butterflies that won raves from lepidoptery's literary champion, Vladimir Nabokov, 70 years after its publication.

他们中包括萨缪尔斯卡德，他命名了黑脉金蝴蝶，写了一本关于北美蝴蝶的三卷的权威著作，这部书出版70年后令鳞翅类昆虫的文学巨匠弗拉基米尔•纳博科夫惊叹不已。