5 
INSECTICIDES FOR EXTERNAL BITING INSECTS (FOOD POISONS). 
THE ARSENICALS: PARIS GREEN, SCHEELE’S GREEN, ARSENITE OF LEAD, AND LONDON 
PURPLE. 
The arsenical compounds have supplanted, practically, all other sub- 
stances for the insects falling under this heading.' The two arsenicals in 
most common use, and obtainable everywhere, are Paris green and Lon- 
don purple. The other two arsenicals mentioned, viz, Scheele’s green 
and arsenite of lead, are less known and not so easily obtainable, but in 
some respects are better than the first-mentioned poisons, as will be 
shown later. The use of powdered white arsenic is not recommended on 
account of its great liability to scald foliage as well as for the fact that 
it is apt to be mistaken for harmless substances. The arsenicals men- 
tioned have the following characteristics: 
Paris green is a definite chemical compound of arsenic, copper, and 
acetic acid (known as the aceto-arsenite of copper), and should have a 
nearly uniform composition. It is a rather coarse powder, or, more 
properly speaking, crystal, and settles rapidly in water, which is its 
greatest fault. It costs about 20 cents a pound. 
Scheele’s green is similar to Paris green in color, and differs from it 
only in lacking acetic acid; in other words, it is a simple arsenite of 
copper. It is a finer powder than Paris green, and therefore more easily 
kept in suspension, and has the additional advantage of costing only 
about half as much per pound. It is used in the same way and at 
about the same strength as Paris green and London purple. 
London purple is a waste product in the manufacture of aniline dyes 
and contains a number of substances, chief of which are arsenic and 
lime. It is quite variable in the amount of arsenic and is not so 
effective as the green poisons and is much more apt to scald unless 
mixed with lime. It comes as a very fine powder, and is more easily 
kept in suspension than Paris green. It costs about 10 cents a pound. 
Arsenite of lead is prepared by combining, approximately, 3 parts of 
the arsenite of soda with 7 parts of the acetate of lead (white sugar of 
lead) in water. These substances when pulverized unite readily and 
form a white precipitate, which is more easily kept suspended in water 
'Hellebore.—The powdered roots of the white hellebore (Veratrum viride) are often 
recommended and used as an insecticide, particularly as a substitute for the arsenites. 
This substance is useful when a few plants only are to be sprayed, as in yards and 
small gardens, but is too expensive for large operations. It kills insects in the same 
way as the arsenicals, as an internal poison, and is less dangerous to man and the 
higher animals; but if sufficient be taken it will cause death. It is particularly 
effective against the larvie of sawflies, such as the cherry slug, rose slug, currant 
worms, and strawberry worms. 
It may be applied as a dry powder, preferably diluted with from 5 to 10 parts of 
flour, and dusted on the plants through a muslin bag or with powder bellows. The 
application should be made in the evening, when the plants are moist with dew. 
Used as a wet application, it should be mixed with water in the proportion of 1 ounce 
to the gallon of water and applied as a spray. 

