12 BULLETIN 278, U. S. DEPARTMENT OF AGRICULTURE. 
water. Arsenate of calcium, homemade (2), was prepared from 
sodium arsenate and calcium chlorid, the method of procedure 
being the same as for arsenate of calcium, homemade (1), and was 
used at the same strength. 
Lead chromate, commercial, was used at the rate of 8 pounds to 
50 gallons. Lead chromate, homemade, was prepared by dissolving 
2 ounces of lead nitrate in one lot of water and 1 ounce of potassium 
bichromate in another lot of water. The two solutions were then 
mixed, and a dense yellow precipitate of insoluble lead chromate was 
formed. The amount of lead chromate formed is 2 ounces, and the 
strengths at which the material was used in these experiments were 
based on the amount of lead chromate formed. 
H. Maxwell-Lefroy and R. S. Finlow state the following in regard 
to the use of the above form of homemade lead chromate as an insecti- 
cide : 1 
During this year we have applied this compound to a great variety of crops. We 
have sprayed them till every leaf was yellow. The poison has remained on for oveT 
three weeks, thickly on the leaves, which were uninjured. Sprayed on to crops at- 
tacked by caterpillars, the caterpillars are killed, and the results obtained have beer, 
excellent. We have used this at 1 pound in 32 gallons. At this strength it is entirely 
safe, poisons caterpillars, and acts as a very powerful deterrent. * * * Lead 
chromate has not the poisoning effect of Paris green, for instance, which can be applied 
at 1 pound in 200 gallons, but it has a poisoning effect comparable with that of lead 
arsenate, and is, in our experience, a perfect substitute. 
As a result of this success with the use of this preparation as an 
insecticide in India, thorough tests were made with it in experiments 
conducted during the season of 1913. 
Experiment VI. 
ARSENATE OF LEAD VERSUS ARSENATE OF CALCIUM AGAINST LARVAE OF THE TENT 
CATERPILLAR. 
In this experiment arsenate of lead paste and the different forms 
of arsenate of calcium were tested in comparison against newly 
hatched larvae of the tent caterpillar. The results of this test are 
shown in Table VI. 
Arsenate of lead alone killed the 50 larvae in each of the two lots 
in 5 days, with 0.04 square inch of foliage consumed. Combined 
with lime-sulphur it required 2 days longer to kill, but only 0.01 
square inch of foliage was consumed. 
Arsenate of calcium, homemade (1), prepared from sodium arse- 
nate and calcium acetate, killed the larvae in 5 to 7 days, with 0.05 
and 0.06 square inch of foliage consumed when used alone, and in 5 
days when combined with lime-sulphur, with 0.02 square inch of 
foliage consumed. Arsenate of calcium, homemade (2), gave prac- 
tically the same results. 
1 Maxwell-Lefroy, H., and Finlow, R. S. Inquiry into the insecticidal action of some mineral and 
other compounds on caterpillars. In Memoirs Dept. Agr. India, Ent. Ser., v. 4, no. 5, p. 269-327, 1913. 
