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Sticker of Japanese giant water bug
Bug card No. 2389 of 4,939

Japanese giant water bug

Appasus japonicus
Eats: Other bugs and small animalsTrue bugs and cicadasPonds, rivers and shores6 legs

The Japanese giant water bug is a flat brown bug that lives in ponds in Japan and Korea. It has strong front legs for grabbing food. It is famous because the father carries the eggs on his back.

Lives in
Japan and Korea, in ponds, lakes, marshes and rice fields
Length
1.6 to 2.1 cm (0.63 to 0.83 in)
Top speed
about 2.4 km/h (1.5 mph)
Swimming, estimate
Can it hurt you?
Can bite
It can give a painful poke with its beak if picked up. Watch it in the water and do not grab it.
What does it eat?
It grabs water snails and water insects with its front legs, then sucks out their insides with its sharp beak.
For real!Photo of Japanese giant water bug
Picture by wasabinouta. CC BY 2.0, via Wikimedia Commons.

How big is it?

How long is it?

Japanese giant water bug about 2.1 cm long (0.83 in)A grain of rice about 6 mm (0.24 in)A toy building brick about 3.2 cm (1.3 in)A crayon about 9 cm (3.5 in)
as long as 4 grains of rice in a rowcould swim the length of a bathtub in 3 secondsmoves 32 times its own body length every second

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cool stuff

Fun facts

1

The mother glues her eggs onto the father's back. He looks after them until they hatch.

2

One father can carry up to about 150 eggs, sometimes from several different mothers.

3

Mothers like to choose a father who is already carrying eggs.

4

The eggs take about a month to hatch in spring, but only about a week in warm summer water.

5

Its ponds are disappearing, so it now often lives in rice fields. It is endangered in Japan.

you asked

Most asked questions about Japanese giant water bug

?Is the Japanese giant water bug dangerous?

It can poke with its beak if grabbed, which hurts, but it is not dangerous.

?Why does the father carry the eggs?

The mother glues them on his back and he keeps them safe until they hatch.

?How big is the Japanese giant water bug?

It is about 16 to 21 millimetres long.

For bug experts

Scientific name
Appasus japonicus
Group
True bugs and cicadas
Family
Belostomatidae
Classification
Insecta > Hemiptera > Belostomatidae
Lives on
Asia

Where the facts come from

  1. Appasus japonicus (Wikipedia, CC BY-SA 4.0): what it looks like, where it lives, what it eats, sizes and fun facts, retold in simple words.
  2. Picture by wasabinouta. CC BY 2.0, Wikimedia Commons. The sticker of this bug is drawn from this picture.

If we got something wrong, sorry, we are bug fans, not a science journal. Tell us at [email protected] and we will fix it.

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