208 



AGRICULTURE ON THE PACIFIC SLOPE 



second hangs from the surface, and moves downward more 

 easily than upward, as though it were heavier than the water. 

 Notice how often the wrigglers come to the surface to 

 breathe. Notice also the curious breathing organ which 

 looks like a sort of tail. You will be able to see how the 

 wriggler sheds its skin two or three times as it grows 

 larger and finally comes to look as if it were coiled up at one 



end. It is then a pupa (figure 

 121). After remaining for some 

 days in this condition, the skin 

 splits and the winged mosquito 

 comes out. 



Place a little kerosene or 

 crude oil on the top of the water 

 containing the wrigglers; how 

 long do they live? Find out 

 whether tadpoles or fish will 

 eat them. (California Experi- 

 FIG. 121. Pupa of mosquito. ment Station, Bulletin 178, 1906.) 



FLIES 



House flies breed in stables or in places where there is 

 garbage, and the only way to get rid of them is to keep 

 such places clean. From their breeding places they 

 come into the house, often carrying disease germs which 

 they scatter wherever they walk. Read what is said 

 about flies on page 262 (figure 155). 



As the fruit fly chooses a less disagreeable place to breed, 

 we will study it instead of the house fly. A tumbler half 

 full of fruit juice on which a piece of blotting paper floats 



