In nature, you may see many insects(昆虫) and animals of different colours. Have you ever wondered why?

    Locusts(蝗虫) are super delicious food for birds, but it is not always an easy job for birds to catch them. It is neither because locusts are good jumpers or runners nor because they are smarter than their enemies(敌人). The reason is that the colours of locusts change with the colours of crops(庄稼). When crops are young, locusts look green. But when autumn comes, locusts change to the yellow and brown colour as crops do.

    Brown bears, tigers and other animals move quietly through forests. Their enemies can't see them easily. This is because they have colours similar to the trees. For the same reason, polar bears that live on a land of snow and ice are white. Butterflies and bees living among the flowers are colourful like flowers. Soil insects are mostly dark-coloured and they live under the soil(土壤) in a dark and wet environment. However, insects with colours different from plants can easily be found and eaten by others. So in order to survive, they have to hide themselves in the daytime and appear only at night.

    Have you ever noticed some even stranger acts? The ink fish in the sea can send out some black ink when it faces danger. As the ink spreads over, its enemies will find themselves suddenly in a dark world. At the same time the ink fish immediately swims away. That is how it keeps itself safe though it is not strong at all.

    What do three hearts, eight arms, and one huge brain add up to? An octopus(章鱼)— a sea animal that can do amazing things.

    Octopuses are very smart. They can learn new things just like humans. They've even learned a few skills to get themselves out of dangerous situations. Octopuses don't have teeth or sharp(锋利的) claws to protect themselves. Instead, they use more clever ways to fool their enemies. Octopuses like to hide themselves in the sand on the bottom of the ocean floor. It can change the colour of its skin to match the sand. And this colour change happens in less than a minute.

    Some octopuses like to stay near rocks in shallow water. They can make themselves fit into small spaces between the rocks to get out of reach of their enemies. Another way an octopus can hide is by shooting ink. The ink forms a cloud that hides the octopus. By the time the ink clears, the octopus has swum away or hidden.

    If an octopus is in danger, it can make itself look like a sea snake. It will hide itself in the sand, leaving two arms outside. It will change the colour of those arms to match a sea snake. But what if there's no time to hide? It can break off one of its arms. The arm will then change colours and keep moving around in the water to take the enemy's attention away while the octopus swims away to safety.

Don't worry though. The arm will grow back.

    A kind of octopus in called the blue-ringed octopus. It is tiny. But the enemies know they should stay away because it is very poisonous and can kill animals much larger than itself, including humans.

    So the next time you see an octopus in the aquarium, remember that inside that oversized head is a very large brain, making it a clever addition to the sea.

— Thanks.