Fireflies, glowworms and many other animals can make their own light. They do this by making and mixing chemicals outside/inside their bodies.

Scientists call this light bioluminescence (pronounced bio-loom-in-ESS-sense). This is a mix of bio, a Greek word meaning life, and lumin, a Latin word meaning dark/light. Animals that make their own light are called bioluminescent (bio-loom-in-ESS-sent).

Some animals use the light they make to hunt. Some use light to send away/attract mates. Many use it simply to see where they're going in the dark!

Flashing fireflies

During the day, fireflies look like ordinary beetles. But at night, they give off a very powerful glow that they can switch on and off.

Fireflies use their lights to find mates. Males flash in one pattern and females flash in another. This means fireflies don't make embarrassing mistakes when looking for a date.

Male fireflies have wings but females don't. Males fly about, flashing on and off. When the females see their signals, they flash for the males to come over.

There are about 2,000 different species of firefly living around the world. Species can tell each other apart because they have different flashing patterns.

However, some fireflies like to eat other types of fireflies. They flash like a friendly mate and then eat whoever comes to visit.

True or false?

Male fireflies have wings but females don't.

Fireflies only live in Asia.

Male and female fireflies flash in different patterns.

All fireflies are vegetarian.

Glowing colossal squid

Find words that mean the following:

giant, arm, victim

The colossal squid lives in the Antarctic Ocean. The water there is cold. In the summer, it's just 10 degrees Celsius. In the winter, it can be as low as minus 2 degrees.

The colossal squid grows up to 14 metres long. If it stood up straight, it could look into the window of a fifth-floor flat.

This giant animal has 10 tentacles. Each tentacle has suckers filled with small teeth. The tentacles also have sharp hooks. If this squid catches you, it's hard to make it let go.

The colossal squid hunts smaller squid and big fish that live more than a kilometre under the surface. They sometimes dive up to 2.5km below the surface.

There is very little sunlight this far down in the ocean. The colossal squid can make its own light but we don't really know how it is used.

Some scientists think it uses its light to attract prey. Others say the light attracts mates. Until we can dive down and see what it does, we can only guess.

What do you think the colossal squid uses its bioluminescence for?

The fish that fishes for fish

Fill in the gaps with the following words:

dark, food, prey, bright

The anglerfish has a long spine on its forehead. The spine has a knob on the end. Scientists call this special spine an esca (pronounced ESS-ka).

Anglerfish that live in the ocean deeps where it is very _______ have escas that glow. This ______ shining light helps them catch their _______.

The anglerfish waves its esca, and other fish mistake it for a worm or other ______. They come for a closer look and are eaten by the anglerfish.

There are more than 200 species of anglerfish living in oceans around the world. They have different names in different places. Anglerfish are also called frogfish, goosefish and seadevils.

See for yourself

Many of the animals that make their own light live very deep in the ocean or in countries far away from Hong Kong.

One way to learn more is to read up on bioluminescent creatures on the internet. But there are a few you can see in Hong Kong if you're patient and can persuade a parent or teacher to take you out at night.

The easiest to spot are fireflies and glowworms. Fireflies lay their eggs in streams or rivers, so look for them near clean, fresh running water.

Firefly larvae and adult fireflies have been spotted in Tai Po Kau Headland in Tai Po. You can also try looking in rivers and swamps.

If you go to the beach, look out for flashes of blue-white light in the water. This is created by bacteria called dinoflagellates (pronounced die-noh-FLA-gel-ates). Dinos can be so bright their glow is seen by satellites.

You might also find seed shrimp or clam shrimp on the beach. If you crush them, they give off a bright light.

Also, Ocean Park has a flashlight fish.

During the second world war, Japanese soldiers carried dried powdered seed shrimp. If they needed to see in the dark, they would crush them in water and use the mixture as a torch.

fab fact!

Baby fireflies or firefly larvae also glow. Because they are round and look like worms, they are called glowworms.

fab fact!

The Tsukiyotake mushroom that grows in Japan and East Asia shines in the dark. This fungus contains the same chemicals that make fireflies shine.

now do this

Answer the following questions. To test your memory, try answering without referring to the text. If you can't remember the details, read the piece again.

1 Creatures that make their own light are ...

a. bioluminescent

b. living lights

c. extinct

2 Fireflies like to live near ...

a. oceans

b. clean freshwater

c. mud puddles and drains

3 Baby fireflies are also called ...

a. glowworms

b. lightning bugs

c. firefleas

4 There are ____ species of anglerfish.

a. 20,000

b. 2,000

c. 200

5 Colossal squid live in ...

a. the Indian Ocean

b. the Antarctic Ocean

c. the North Sea

6 In the past, Japanese soldiers used _____ as torches.

a. fireflies

b. anglerfish

c. seed shrimp

compare!

Normal light bulbs waste 90 per cent of the energy they use. Only 10 per cent is turned into light. The firefly turns 90 per cent of its energy into light

Answers:

Nature's animal lamps: deeps, inside, dark, attract

Flashing fireflies: true, false, true, false

Glowing colossal squid: colossal, tentacle, prey

The fish that fishes: dark, bright, prey, food

Quiz: 1. a; 2. b; 3. a; 4. c; 5. b; 6. c