Why, you may wonder, should spiders be our friends ? Because they destroy so many insects, and insects include some of the greatest enemies of the human race. Insects would make it impossible for us to live in the world; they would devour all our crops and kill our flocks and herds, if it were not for the protection we get from insect-eating animals. We owe a lot to the birds and beasts who eat insects but all of them put together kill only a fraction of the number destroyed by spiders. Moreover, unlike some of the other insect eaters, spiders never do the least harm to us or our belongings.
Spiders are not insects, as many people think, nor even nearly related to them. One can tell the difference almost at a glance for a spider always has eight legs and an insect never more than six.
How many spiders are engaged in this work on our behalf ? One authority on spiders made a census of the 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 something like 6,000,000 spiders of different kinds on a football pitch. Spiders are busy for at least half the year in killing insects. It is impossible to make more than the wildest guess at how many they kill, but they are hungry creatures, not content with only three meals a day. It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year would be greater than the total weight of all the human beings in the country.
T. H. GILLESPIE Spare that Spider from The Listener
New words and expressions 生词短语
flocks and herds 牛群和羊群
／flCk/ the birds of the same feather flock together.物以类聚，人以群分
you are the same flock.也可指人
herd多指牛群 cowherd cowboy throng and crowd swarm
owe /[U/ vt.感激 欠 i owe you. i owe you a big favor. 欠 issue
oblige indebt appreciate----常用口语词 正式：grateful thankful
beast /bi: st/ n 兽 形容人野蛮无比，不能用animal 形容
creature可以指小孩，女人，不用于男性．
fraction / ＇frAkF[n/ n.小部分 分数，小数 a fraction of rice will suffice
on one＇s behalf 代表．．．利益
I beat you on your behalf.我打你是为你好 on behalf of somebody /something
e.g on behalf of chinese government on behalf of ＝represent
authority /C:＇WCriti/ n.权威 authorize批准 authoritative权威性的 authoritarian独裁的
－tarian带有这种词缀的词都是坏词 dictator独裁者 dictatorial独裁的
authorities １．权威（可单数可复数） ２．当局（复数）
census /sens[s/ n.统计数据 the fifth national population census. censor审查
censorious 挑剔的，挑刺的
acre /＇eik[/ n.英亩 １acre＝４０４７square meters
football pitch 足球场 football yard football court football field
be content with 满足于 满足作表语，不能出现定语结构
He is content with status quo. contented heart :心满意足的人
spare /spZ[/ v. 不伤害，宽恕 spare me He doesn’t spare himself.
I spare no efforts to learn english.( spare no efforts: 不遗余力作什么)
Notes on the text 课文注释
why, you may wonder－you may wonder why插入语 先不管插入语，弄清句子结构
you may wonder why spiders should be our friends？插入语位置不固定
why以疑问句 开头
why,you may wonder,the problem of pollution befalls human beings.
why,you may wonder,one of my friends is so kindhearted.
destroy程度比damage要重得多，片甲不留，消灭光 tear into pieces
greatest enemies:天敌 dying enemy crying enemy dear enemy
human race:人的种族，一般不加复数，表示一个总称词
impossible 和possible 永远不要以人开头
It is impossible for somebody to do something.
likely可以以人做主语。i am likely to go. probable 也不以人做主语
they would表示假设
devour狼吞虎咽devour the food
make a cake of myself make a god of myself devour the book
it虚拟语气 前面是主句，下面是条件句
前面一般的加动词devour,后面用一般过去时
If it were not for:如果这不是因为
I would not survive if it were not for his timely help.
but for 一定是虚拟语气 ＝if it were not for
owe感激，欠 i owe you.
引出主题 all of them put together:把他们堆到一起 谓语动词是kill
destroyed后置定语，重心转到spider
参考译文
你可能会觉得奇怪， 蜘蛛怎么会是我们的朋友呢？因为它们能消灭那么多的昆虫，其中包括一些人类的大敌，要不是人类受一些食虫动物的保护，昆虫就会使我们无法在地球上生活下去，昆虫会吞食我们的全部庄稼，杀死我们的成群的牛羊。我们要十分感谢那些吃昆虫的鸟和兽，然而把它们所杀死的昆虫全部加在一起也只相当于蜘蛛所消灭的一小部分。此外，蜘蛛不同于其他食虫动物，它们丝毫不危害我们和我们的财物。
许多人认为蜘蛛是昆虫，但它们不是昆虫，甚至与昆虫毫无关系。人们几乎一眼就能看出二者的差异，因为蜘蛛都是8条腿，而昆虫的腿从不超过6条。
有多少蜘蛛在为我们效力呢？一位研究蜘蛛的权威对英国南部一块草坪上的蜘蛛作了一次调查。他估计每英亩草坪里有225万多只蜘蛛。这就是说，在一个足球场上约有600万只不同种类的蜘蛛。蜘蛛至少有半年在忙于吃昆虫。它们一年中消灭了多少昆虫，我们简直无法猜测，它们是吃不饱的动物，不满意一日三餐。据估计，在英国蜘蛛一年里所消灭昆虫的重量超过这个国家人口的总重量。
