2 BULLETIN 1439, U. S. DEPARTMENT OF AGRICULTURE 
(9, p. 9, 15) in 1920 stated that he had found either calcium caseinate 
or sea-moss stock, prepared by boiling the moss in water, to increase 
the adhesiveness of certain insecticides. Smith (8, p. 7) in 1922 
stated that the use of caseinate as a spreader in the codling moth spray 
and the dormant lime-sulphur spray, recommended by him for the 
control of orchard insects in Idaho, adds materially to their effec- 
tiveness. Headlee (3, p. 294) found in 1923 that casein, and also 
flour, retain more than twice as much lead arsenate as is retained 
when no adhesive is used. 
In 1921 the writer began a series of experiments along this line, 
his effort being to find, if possible, some substance which, when added 
to spray mixtures, would cause them to spread and adhere more 
strongly to foliage sprayed with them, especially foliage of a glossy 
nature. 
WHY AN ADHESIVE IS NEEDED 
Spraying operations against the gipsy moth begin about May 1 in 
New Jersey, and much later in New England, and continue for four 
to six weeks. All of the material is applied with high-power sprayers, 
and many tons of arsenate of lead are used annually in the infested 
area. The areas to be sprayed are carefully planned out, the crews 
for each sprayer selected, the necessary material obtained, and the 
time required to cover these areas carefully determined in order that 
the spraying may be done promptly enough to be effective. There 
are many drawbacks, however, which more or less upset these plans, 
among them being bad weather, when no spraying can be done; 
at other times, when large areas are sprayed, frequent rains wash 
practically all of the poison from the foliage, and a second, and some- 
times a third, spraying is necessary. In such cases the cost of spray- 
ing the area is doubled or tripled, and where large areas are concerned 
the expense is much greater. Further, to be effective the spray 
mixture used in gipsy moth work must be stronger than is ordinarily 
used against most leaf -feeding insects and, when applied to the 
foliage, should for maximum efficiency remain there during the entire 
larval season of the gipsy moth. From these facts it can be seen 
that a really good adhesive would economize materials and labor 
and save much valuable time. 
PRELIMINARY EXPERIMENTS 
IN 1921 
In 1921, 1922, and 1923 the writer's experiments were conducted 
in a small way, with small hand sprayers, compressed-air sprayers, 
or an ordinary barrel pump equipped with two paddles at the bottom 
of the barrel for agitation. In 1921 a number of combinations were 
tried. The mixtures were sprayed upon glass plates and allowed to 
dry thoroughly, after which they were tested by rubbing lightly 
with the fingers and by placing them beneath a stream of lightly 
running water, striking with about the same force as would be en- 
countered in a moderately heavy rainstorm. In one case linseed oil 
was the adhesive tested; in every other case two ingredients were 
combined to make the adhesive. Following are the results recorded, 
the specified quantities of the ingredients in each case being mixed 
with 100 gallons of water and 63^ pounds of arsenate of lead: 
