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 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.