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Lesson 2 |
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Spare that spider |
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How much of each year do spiders spend killing insects? |
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Why,you may wonder,should spiders be our friends? |
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Because they destroy so many insects, and insects include some of the greatest enemies of the human race. |
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Insects would make it impossible for us to live in the world; |
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they would devour all our crops and kill our flocks and herds, |
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if it were not for the protection we get from insect-eating animals. |
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We owe a lot to the birds and beasts who eat insects |
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but all of them put together kill only a fraction of the number destroyed by spiders. |
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Moreover,unlike some of the other insect eaters, |
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spiders never do the least harm to us or our belongings. |
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Spiders are not insects,as many people think,nor even nearly related to them. |
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One can tell the difference almost at a glance, |
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for a spider always has eight legs and an insect never more than six. |
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How many spiders are engaged in this work on our behalf? |
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One authority on spiders made a census of the spiders in a grass field in the south of England, |
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and he estimated that there were more than 2,250,000 in one acre; |
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that is something like 6,000,000 spiders of different kinds on a football pitch. |
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Spiders are busy for at least half the year in killing insects. |
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It is impossible to make more than the wildest guess at how many they kill, |
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but they are hungry creatures,not content with only three meals a day. |
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It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year |
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would be greater than the total weight of all the human beings in the country. |