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 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 insect never more than six.#
How many spiders are engaged in this work no 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.&