Monarch butterflies from eastern Canada make the most amazing journey in the insect world. Each year, this butterfly travels about 3000miles to its winter home in central Mexico(墨西哥). How can it fly so far? And why does it make this long and dangerous trip? Scientists still don't have an answer.

 For many years, people in Mexico wondered where the orange-and-black butterflies came from every winter. Then, in 1937, a scientist started to follow and study the butterflies. For the next 20 years, he discovered that one butterfly started its journey in Canada. Four months later, it arrived in Mexico.

 The length of the butterflies find their way back to the same place? Another amazing thing is that the butterflies always return to the same area in central Mexico.

 How do the butterflies find their way back to the same place? This is an interesting question because only every fourth generation(代) makes the trip south. In other words, the butterfly that travels to Mexico this year is the great-great-grandchild of the butterfly that traveled there last year.

 Each year, four generations of a Monarch butterfly family are born. Each generation of the family has a very different life. The first generation is born in the south in late April. It slowly moves north, reproduces(繁衍), and then dies. On the trip north,two more generations are born, reproduce, and die. Each of these generations of butterflies is born. This generation has a much longer life. It lives for about eight months. This generation of butterflies makes the amazing journey back to the winter home of its great-great-grandparents. The butterflies spend the winter there, and in the spring they reproduce and then die. Their offspring will be the first generation of the next circle of life.

 Today, people are still studying the Monarch butterfly. But they are not clear about everything.

    Do you know why different animals or pests have their special colors? Colors in them seem to be mainly used to protect themselves.

Some birds like eating locusts (蝗虫), but birds cannot easily catch them. Why? It is because locusts change their colors with the change of the colors of crops. When crops are green, locusts look green. But as the harvest time comes, locusts change into the same brown color as crops have. Some other pests whose colors are different form plants are easily found and eaten by others. So they have to hide themselves for lives and appear only at night.

    If you study the animals' life, you'll find the main use of colors is to protect themselves. Bears, lions and other animals move quietly through forests. They cannot be easily seen by hunters because their colors are much like the trees.

    Colors are useful not only on the land, but also in the sea. A kind of fish in the sea can give out a kind of black liquid (液体) when the fish face danger. The liquid spreads over quickly, so they cannot be found by their enemies and can quickly swim away. That is why they live safely though they are not strong at all.

    What was discovered by accident? The answer is penicillin(青霉素). It kills germs. By killing germs, it saves lives. Suppose you are sick. You go to a doctor. She examines you. She says you have a "staph" infection(葡萄球菌感染). She gives you some medicine. You take it. The medicine knocks out the staph. Soon you are well. Before penicillin, this would not happen. Staph was almost sure death.

    Everyone wanted a medicine. Laboratories worked day and night. They grew the staph in small dishes. Then they tried to kill it. Nothing worked.

    The laboratory dishes had covers on them. They kept things from falling into dishes. Molds(霉菌)were a big worry. They are always in the air. You can't see them. They're too small .There are thousands of different molds. Molds can make an experiment (实验)fail. That's why dishes are covered.

    Dr. Alexander Fleming was working to kill the staph germ. He worked for years. One day he took a cover off a dish. He looked inside. There was a thick growth of staph germ. There was also some mold. Then he saw something strange. Where the mold was, there was no growth of staph. This is what Fleming probably thought. "By accident, I found a mold to kill the dreaded staph."

    This is how penicillin was found. But here's the real miracle(奇迹). There are thousands of kinds of molds. But only one kind can kill staph. The mold must have fallen into the dish a few days before. The cover was probably off only a few seconds(秒). In those few seconds the right mold fell into the right dish. Another mall might have thrown the dish away. But Fleming was very careful and smart. He understood what the mold did. How lucky the humans were!

    They say music is universal, and it seems to be true since wherever we go, we see people listening, playing or dancing to it. We tend to think that music is larger than our cultural differences and shows the deeper connections between us.

    But according to a recent study published in the Current Biology, music doesn't speak to everyone. There is a condition, the researchers argue, called "musical anhedonia". They say that those who have this condition may have few abilities to experience pleasure from music.

    For the study, 30 people listened to the same, mostly classical music pieces. They were then asked to complete a questionnaire on how they felt about the music. At the same time, the researchers measured their heart rate and skin reaction, which are considered physiological measures of feelings.

    According to the researchers, most of the people in the study got pleasure from the music. They had a quicker heartbeat and sweatedmore. However, a small number of them had very little and even no pleasant feeling while they were listening to the music. These people had none or very few of the physical signs which the others in the study experienced.

    The researchers say that this means people have different abilities to enjoy music and that "there are people who specifically can't enjoy music at all"

    To study the condition more deeply, another group of scientists, at Columbia University, US, researched brain activities. They found that the key is the blood flow to the reward system in the brain. People who got less pleasure from music had comparatively lower blood flow to areas involved in the reward system of the brain when they were listening to music.

    The lower blood flow makes it more likely that the brain's "reward system" will be inactive. And it will produce less of the "pleasure chemical" dopamine. As a result, people get less pleasure from music.

    If the research is correct, according to National Public Radio, there are simply people who just don't get music. They may get pleasure from many things, but a good tune isn't one of them.

    Why do we like drinking water from plastic bottles? Some people think it is healthy and clean. Others drink bottled water because it's easy--you can carry it around with you. In hot countries, like Greece, we often buy bottles of cold water in the summer.

    However, making tots of plastic is not a good idea for many reasons. First of all, we need a lot of oil for plastic products. We usually use oil as a source(资源) of energy. If we reduced the number of bottles we made, we wouldn't need so much oil. Plastic bottles also pollute the environment. If we recycled all our plastic bottles, we wouldn't need so much space for rubbish dumps. But in Greece, we don't recycle much of the plastic we use. In 2006, Greeks recycled only about 10% of plastic waste. The rest became rubbish on land and in rivers and seas.

    So next time you want to throw away a plastic bottle in the litter bin, stop and think. If you recycled it, you would help the environment. But what can you do when there isn't a recycling bin near you? Well, there are lots of useful ways that you can use your bottles again. For example, an empty bottle makes a great piggy bank for your pocket money, and if you cut a bottle in half, you will have a plant pot. Go green! You can make a difference.