[al:新概念英语（四）] [ar:MP3 同步字幕版（英音）] [ti:Spare That Spider] [by:更多学习内容，请到chazidian.com搜索“新概念”] [00:01.47]Lesson 2 [00:03.26]Spare that spider [00:12.39]How much of each year do spiders spend killing insects? [00:20.01]Why,you may wonder,should spiders be our friends? [00:24.45]Because they destroy so many insects, and insects include some of the greatest enemies of the human race. [00:32.57]Insects would make it impossible for us to live in the world; [00:37.02]they would devour all our crops and kill our flocks and herds, [00:41.92]if it were not for the protection we get from insect-eating animals. [00:47.87]We owe a lot to the birds and beasts who eat insects [00:52.38]but all of them put together kill only a fraction of the number destroyed by spiders. [00:58.64]Moreover,unlike some of the other insect eaters, [01:02.57]spiders never do the least harm to us or our belongings. [01:08.18]Spiders are not insects,as many people think,nor even nearly related to them. [01:15.83]One can tell the difference almost at a glance, [01:19.22]for a spider always has eight legs and an insect never more than six. [01:26.94]How many spiders are engaged in this work on our behalf? [01:31.39]One authority on spiders made a census of the spiders in a grass field in the south of England, [01:38.13]and he estimated that there were more than 2,250,000 in one acre; [01:45.46]that is something like 6,000,000 spiders of different kinds on a football pitch. [01:52.30]Spiders are busy for at least half the year in killing insects. [01:58.09]It is impossible to make more than the wildest guess at how many they kill, [02:03.38]but they are hungry creatures,not content with only three meals a day. [02:09.16]It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year [02:15.99]would be greater than the total weight of all the human beings in the country.