Passage Three
The Waitomo Caves are one of the most famous places to visit in New Zealand. Each year,around half a million people visit the caves.Why do so many people visit these caves?It's because they are so different from other caves around the world.
From bat dens in Texas to sinkholes in Australia,caves are usually dark places.The Waitomo Caves don't follow this rule,though.The Waitomo Caves are lit up by thousands of small bugs that glow in the dark.These glowworms line the cave walls and ceiling,filling the caves with a soft blue-green light. Because of this light,people can see the beautiful rock formations throughout the caves.
The glowworms that line the cave are not actually worms—they're baby flies.The baby flies begin glowing bright blue soon after they hatch from eggs in the cave.They use this light to attract other bugs that are lost in the cave.When the lost bugs see the light,they go toward it.Then the glowworms can catch the bugs and eat them.And when the glowworms are very hungry,they can shine their lights even brighter to catch even more bugs.
The glowworms have made the Waitomo Caves a must-see stop on any vacation to New Zealand.You can hike through the caves or take a slow-moving boat ride through them.The natural glow of the caves shows how magical nature can be.If you're ever in New Zealand,you may want to check these caves out!
问题:Why do the glowworms in the Waitomo Caves glow?