The passage is mainly about

the puzzle of a long migration that no single butterfly completes (The passage focuses on the mystery of how monarchs make a multi-generation migration they were never taught.)

Who completes the trip back north?

The children and grandchildren of those that flew south (The text says the butterflies that go south are not the ones that return; 'their children and grandchildren' continue.)

Why is the monarchs' sense of direction described as a puzzle?

They were never taught the route, yet still find their way (Their parents die before them, so they cannot be taught; yet they find the route, which is why it puzzles scientists.)

In this passage, 'generations' refers to

the successive parents, children, and grandchildren in the family (The word follows 'their children and grandchildren', marking steps in a family line.)

The Long Flight of the Monarch: Level 3 Reading Comprehension Questions

Each autumn, monarch butterflies leave the cooling fields of the north and travel enormous distances to spend the winter in warmer forests far to the south. For an insect that weighs less than a paperclip, the journey is astonishing. Yet the strangest part is not the distance but who makes it.

No single butterfly flies the whole round trip. The monarchs that travel south in the fall are not the same ones that return. On the way back north in spring, the butterflies breed, lay eggs, and die, and it is their children and grandchildren that continue the trip. Several generations may pass before the family reaches the northern fields again.

This raises a hard question. If the butterflies heading south have never seen the winter forest, how do they know where to go? They were not taught the route, for their parents died long before. Somehow the direction is written into them from birth, carried in their bodies rather than learned. How a tiny brain stores such a map remains one of nature's open puzzles.

Comprehension questions