# Deadly glow: do insect-eating plants use light to attract their victims?

An ant creeps up the side of a pitcher plant. The insect doesn't know it, but it's walking into a trap. The plant's cup-shaped leaves have a slippery rim. When the ant reaches the edge, it tumbles in and can't escape. The carnivorous plant slowly digests its tasty meal.

How do insect-eating plants lure bugs to their death? Scientists in India recently shed some light on this question.

All Lit Up

Carnivorous plants attract prey using bright colors, sweet nectar, and tempting smells. But scientists wondered if the plants had another trick too.

The scientists knew that plants in the wild soak up ultraviolet (UV) light from the sun. People can't see UV light without special equipment, but insects can. Carnivorous plants could look different to bugs than they do to us.

To find out what an insect might see, the scientists placed a pitcher plant under a UV light in their lab. To their surprise, the light made the rim of the plant glow blue! The scientists wondered: Could the glow act as a signal to attract bugs?

Put to the Test

To test this idea, the scientists headed into the field. There, they covered the rims of some pitcher plants with special paint. The paint blocked UV light, so the plants couldn't glow. The team left other pitcher plants alone.

After 10 days, the scientists returned to see which plants had caught the most ants. They found that the painted plants were nearly empty. The unpainted plants were packed with bugs. It seems that insects really are drawn to the plants' attractive glow!

Investigate It!

Scientists often follow a set of steps to discover new things. First, they ask a question. Then they come up with a possible answer, or hypothesis. Next, they plan an experiment to test their hypothesis. Finally, they collect data and draw a conclusion.

1 What question did the scientists want to answer?

2 Identify the variable and control in their experiment. (A variable is a characteristic that is changed in an experiment. A control is a characteristic that stays the same.)

3 What was the scientists' conclusion?

4 How would you take the experiment further?

1. Does a pitcher plant's glowing rim help it attract insects? 2. The plants with painted rims were the variable. The unpainted plants were the control. 3. The glowing rim helps pitcher plants attract more bugs. 4. Answers will vary.

Lexile Level 760; Guided Reading Level N

OBJECTIVE

Understand how scientists used scientific inquiry to learn about pitcher plants. Then apply inquiry methods to another question.

SETUP

Purchase a set of UV beads online.

1. Bring in various bottles of sunscreen.

* What does SPF stand for? (sun protection factor)

* What does SPF protect us from? (ultraviolet radiation)

* What does a higher SPF number mean? (A higher number means protection for a longer period of time.)

1. Show UV beads. Tell students they contain a chemical that changes color when exposed to UV light.

2. In pairs, students will select one of the following questions to investigate:

* How does time of day affect the color of the beads?

* How do differences in weather at the same time of day affect the color of the beads?

* How does applying sunscreen with different SPFs affect the color of the beads?

* How do different brands of sunglasses affect the color of the beads?

* How do indoor and outdoor light affect the color of the beads?

3. Have students write out a plan of how they will test for and answer their question. Then they can investigate it!

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