Today we're going to discuss the migration patterns of monarch butterflies. Unlike many insects that live only a few weeks, monarchs have a remarkable multi-generational migration. Each year, the eastern population travels up to 3,000 miles from the United States and Canada to central Mexico, where they overwinter in oyamel fir forests. The journey isn't completed by a single butterfly; instead, it takes four generations. The first three generations live only about six weeks, but the fourth generation, born in late summer, has a different physiology. This 'super generation' lives up to eight months and undertakes the entire return journey. Scientists have discovered that these butterflies use a combination of the sun's position and an internal magnetic compass to navigate. However, what's most intriguing is that they have never made the trip before, yet they follow the same routes as their ancestors, suggesting an inherited memory or genetic encoding of the migration path.
❓ 题目 What is the main purpose of the lecture?
A. To explain how monarch butterflies navigate using environmental cues
B. To describe the unique multi-generational migration of monarch butterflies
C. To compare the lifespans of different butterfly species
D. To discuss the impact of deforestation on monarch butterfly habitats
✅ 正确答案
To describe the unique multi-generational migration of monarch butterflies
