304 Reporr oF THE DprpaRTMENT OF ENTOMOLOGY OF THE 
LABORATORY EXPERIMENTS TO DETERMINE THE NATURE OF 
THE ACTION OF THE LIME-SULPHUR-SALT WASH UPON THE 
SAN JOSE SCALE. 
The following experiments, although planned in part at 
Geneva, were largely conceived by Mr. Parrott and were finally 
carried out by him at the Ohio Agricultural Experiment Station. 
Insecticides, broadly speaking, may be divided into two 
classes; first, the poisons or arsenical compounds which act 
only through the stomach, and, second, the contact remedies 
which when applied destroy by suffocation, through the pene- 
tration and sealing up of the insect’s breathing organs. The 
lime, sulphur and salt wash belongs to this latter class, and is 
efficient in the destruction of softbodied and inactive insects; 
in that it contains coroding ingredients designated by the chem- 
ists as principally compounds of lime and sulphur and sodium 
and sulphur, and a large quantity of solid matter which when 
first applied is also caustic and when dried forms a very com- 
pact and adhesive coat, impenetrable by most of the scales. 
Which of the two ingredients is the more important and in what 
way it effects the destruction of the scales, is not known defi- 
nitely. One authority* has offered an opinion that the wash 
is an indirect insecticide; in that it operates more effectually 
against the progeny than the parent insect “through some in- 
gredient or ingredients that remained active, or became active, 
on the trees long after the application.” In other words, pro- 
viding there has been no extensive or rapid, leaching by heavy 
rains immediately following, the wash, after application, has 
within it compounds which become soluble in light rains and 
dews, forming insecticides, which occasionally, if not daily for 
a reasonable time, not only immerse specimens already treated, 
but bathe, and perhaps destroy, the active ‘larve and those 
which have settled, but have not had time to form their pro-- 
tective covering. That the calcium sulphidé will directly kill — 
the’ adult féniales and voun® has been proven conclusively; but 
of the insecticidal properties of the precipitate alone, or of the 
liquids upon the tree resulting from dews and rains, little is 


*Lounsbury. The Agricultural Journal, 20: 771. (June 19, 1902). 
