Why, you may wonder, should spiders be our friends?Because they protect so m

游客2023-12-08  28

问题    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 eat 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】 _____.
nor 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 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 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. [br] 【M7】

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