[00:01.47]Lesson 2
[00:03.26]Spare that spider
[00:12.39]How much of each year do spiders spend killing insects?
[00:20.01]Why,you may wonder,should spiders be our friends?
[00:24.45]Because they destroy so many insects, and insects include some of the greatest enemies of the human race.
[00:32.57]Insects would make it impossible for us to live in the world;
[00:37.02]they would devour all our crops and kill our flocks and herds,
[00:41.92]if it were not for the protection we get from insect-eating animals.
[00:47.87]We owe a lot to the birds and beasts who eat insects
[00:52.38]but all of them put together kill only a fraction of the number destroyed by spiders.
[00:58.64]Moreover,unlike some of the other insect eaters,
[01:02.57]spiders never do the least harm to us or our belongings.
[01:08.18]Spiders are not insects,as many people think,nor even nearly related to them.
[01:15.83]One can tell the difference almost at a glance,
[01:19.22]for a spider always has eight legs and an insect never more than six.
[01:26.94]How many spiders are engaged in this work on our behalf?
[01:31.39]One authority on spiders made a census of the spiders in a grass field in the south of England,
[01:38.13]and he estimated that there were more than 2,250,000 in one acre;
[01:45.46]that is something like 6,000,000 spiders of different kinds on a football pitch.
[01:52.30]Spiders are busy for at least half the year in killing insects.
[01:58.09]It is impossible to make more than the wildest guess at how many they kill,
[02:03.38]but they are hungry creatures,not content with only three meals a day.
[02:09.16]It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year
[02:15.99]would be greater than the total weight of all the human beings in the country.