Insects play an important role in our lifes, we have different ideas about them. Just like a corn have two sides, every thing is relative. Some insects are helpful while other are harmful. Insects sometimes like an angel while sometimes act like a devil. 
      We have known that the bees are hard-working since we were very young. Many flowers are pollinated by bees. However, they sometimes stings. Silkworms are very popular in textile field. They produce the silk. As a matter of fact, I'm not familiar with the insects. But I do hate some insects, such as mosqitos and flies. During the summer time, I find mosqitos quite annoying, they spin around and bite you secretly. It may cause diseases like malaria. Flies sometimes stay on your food and they can tramsfer germs. On the other hand, scientists said that they also have some benefits. 

What is a good insect and what is a bad one? There's no specific answer. But if one of them extincted, the earth will lose her balance. Human beings will be pushed into the edge of danger. Without a doubt, we need all of the insects to create our beautiful planet.

Hi, Yeeyore. You have written a well-organized essay with good supporting details. You should better use "however" instead of "but" at the beginning of a sentence. Pay attention to your misspelled words. Please study different parts of speech. Nonetheless, you did a very good job.