224 AGRICULTURE ON THE PACIFIC SLOPE 



stand up two or three inches above it. The snails are 

 not able to get over the sharp edge, and the plant is 

 thus protected. 



Field mice and gophers. These feed upon the 

 roots and seeds oT plants, and often cause enormous 

 injury on account of the rapid increase in their num- 

 bers. Poison is the best remedy against them. For 



ie gopher we place poisoned baits of carrot, turnip, 

 or raisin in their burrows. There are also good 

 traps. 



Field mice are killed by means of poisoned grain or 

 ground alfalfa. The alfalfa is best, because it is not 

 eaten by the birds. 



HELPFUL INSECTS AND ANIMALS 



There are many insects which help the farmer by 

 destroying other insects. Not only ladybirds (page 

 196), but tiger beetles, lion beetles, and some kinds of 



hornets and flies attack and kill insects which damage 



^ 



plants. Spiders also live on insects. 



Whenever you try to breed insects, you are sure to 

 find that very often in place of the moth or butterfly 

 which you are expecting you get nothing but a lot of 

 small " flies. " These have laid their eggs on or in the 

 caterpillar or worm, and in time they hatch and feed 

 upon it. Then they come out, become pupas, and in a 

 short time turn into winged flies (which may be true flies 



