304 



ELEMENTARY STUDIES IN INSECT LIFE 



tank will be so strong as to injure the foliage, while 

 that at the top will be useless. (See requisites for a 

 spraying-pump. ) 



FIG. 231. The "Pomona" spray-pump, mounted on end of barrel. Used to 

 spray with arsenical mixtures. 



LONDON PURPLE. - This is a by-product in the manu- 

 facture of aniline dyes. It is an arsenite of lime, and 

 contains a variable amount of arsenic. The average 

 may be considered from 30% to 50% arsenic. It is 

 a finer powder than Paris green, likely to remain longer 





