AND ITS RELATION TO ANIMAL LIFE 149 



composition. Turning to insect pests, we 

 may take the case of the cockchafer. 



In Insect World, by Louis Figuier, revised 

 by P. Martin Duncan, F.R.S., p. 465, on the 

 cockchafer 



" Or you may sow in the field rape seed very 

 thickly, which you must then bury by a very 

 deep ploughing, when it is as high as your 

 hand. Cole wort, it is said, kills the larvae, 

 while it at the same time manures the land." 



Miss Ormerod, in one of her works, writing 

 on the cockchafer, says 



" Where the larvae of the cockchafer were 

 placed in a box of soil and covered with half 

 an inch of soil, and then manured with a 

 light dressing of nitrate of soda, the larvae 

 were killed, while a similar lot treated in the 

 same way with a heavy dressing of salt were 

 not injured in the least." 



In this instance we find that the presence 

 of nitrogen, either in the form of a rape crop 

 or as nitrate of soda, is fatal to this insect. In 



