What is the main idea of the passage?

The ant line is organised by smell alone, with no leader and no plan. (The first paragraph says there is no leader and no plan; the rest explains how smell alone produces the line, and the last sentence returns to it.)

According to the passage, what happens after the crumb is gone?

The ants stop adding smell and the trail disappears. (The text says the ants stop adding smell, the old trail dries into the air and disappears, and nobody gives the order to stop.)

Why Ants Walk in a Line: Level 1 Reading Comprehension Questions

Q: In this passage, a "trail" is

a narrow path of smell left on the ground (The passage says the ant "pressed a faint smell onto the ground behind it" and calls that the trail, which later ants follow and strengthen.)

Q: The passage suggests that short routes win because

a short trail is walked more often, so its smell grows stronger (The text says a short trail is walked more often than a long one in the same time, so short routes get stronger and win. No ant chooses; the smell simply builds up faster.)

Drop a crumb on the ground and wait. Before long a single ant arrives, then another, and soon a thin dark line runs from the crumb to a crack in the wall. No ant is leading. There is no plan.

The first ant was wandering. When it found the crumb it turned for home, and as it walked it pressed a faint smell onto the ground behind it. Ants can follow that smell. The next ant crosses the trail, turns onto it, finds the food, and walks home leaving its own smell on top. The trail gets stronger each time it is used.

That is the whole system. A short trail is walked more often than a long one in the same time, so short routes get stronger and win. And when the crumb is gone, the ants stop adding smell. The old trail dries into the air and disappears. Nobody gives the order to stop. The line ends because nothing is left to feed it.

Comprehension questions