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SECOND BOOK. 
12. We have learnt, in most cases, liow we may 
do something towards keeping down their numbers, 
to save our crops. But the best that we can do 
would be of little use if we had to trust entirely to 
ourselves. The fact is we have hosts of helpers. 
Some kinds of insects feed upon others, and 
thousands of birds, lizards, spiders, and other 
creatures are occupied in searching for grubs and 
insects to devour. 
13. Sometimes ticks are the means of spreading 
certain diseases among animals. If they fall from 
the bodies of cattle suffering from disease, they lay 
their eggs in great numbers in the grass, and, when 
other animals are put into the pasture, the young 
ticks crawl upon them, and poison their blood, thus 
causing them to fall ill. 
14. It is most important that ticks appearing on 
the bodies of animals should be destroyed. Old and 
withered grasses, and decaying vegetable matter of 
all kinds, form a cover for these pests, and there- 
fore should not be allowed to remain, but should be 
burnt; and the tick-destroying birds should be 
protected. 
