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om For evaluation only.
Lesson2 Spare that spider
How much of each year do spiders spend killing insects?
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