Why, you may wonder, should spiders be our friends? Because they protect so many insects, and insects include【M1】______ some of the greatest enemies of the human race. Insects would make impossible for us to live in the world; they 【M2】______ would ruin all our crops and kill our flocks and herds, as it were not for the protection we get from insect 【M3】______ -eating animals. We owe a lot for the birds and beasts 【M4】______ who cat insects but all of them put together kill only a fraction of the amount destroyed by spiders. Moreover, 【M5】______ unlike some of the insect-eaters, spiders never make 【M6】______ the least harm to us or our belongings. Spiders are not insects, as many people think, and 【M7】______ or even nearly related to them. One can tell the difference almost at a glance, for a spider always has eight legs but an insect never more than six. How many spiders are joined in this work on our 【M8】______ behalf? One authority on spiders made a census of file spiders in a grass field in the south of England, and he estimated that there were more than 2,250,000 in one acre; that is anything 【M9】______ like 6,000,000 spiders of different kinds on a football pitch. Spiders are busy least half the year in killing insects. It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year would be greater than those of all the human beings 【M10】______ in the country. 【M1】