MISCELLANEOUS INSECTICIDE INVESTIGATIONS. 25 
As will be noted in Table XIV, arsenate of lead as usual killed the 
larva? more quickly than any of the other arsenicals. Arsenate of 
lead paste at the rate of 3 to 50 or 5 to 50 required 12 days to kill 
all of the larvae; when combined with lime-sulphur it required slightly 
longer with a decreased amount of feeding. 
As shown in the preceding experiments of 1914, commercial arse- 
nate of calcium when combined with lime-sulphur is a relatively 
effective poison. Likewise, in this experiment, both lots of the paste 
form in combination witli lime-sulphur killed in 14 days; the pow- 
dered form mixed with lime-sulphur in 14 and 12 days. 
The homemade arsenate of calcium compounds, when employed 
with lime-sulphur, were also relatively effective, especially when their 
low arsenical content is taken into consideration. Homemade arse- 
nate of calcium, formula 1 (As 2 5 = 4.19 per cent), plus lime-sulphur, 
was effective in killing all the larvse of both lots in 18 and 20 days. 
Homemade arsenate of calcium, formula 3 (As 2 5 = 3.93 per cent), 
required 18 and 14 days. 
Experiment XV. 
COMPARISON OF THE KILLING EFFECT OF VARIOUS CONTACT POISONS ON APHIS POMI. 
A series of laboratory tests was made with various contact insecti- 
cides, alone and combined with other materials, against the green 
apple aphis (Aphis pomi De G.). Apple twigs well infested with this 
species were thoroughly sprayed and then placed in separate glasses 
containing water. The results were taken one day after date of 
application. Four tests were made, namely, (1) August 20, p. m.; 
(2) August 21, a. m.; (3) August 21, p. m.; and (4) September 17. 
For test (1) all the materials were freshly combined except No. 17, 
which had been mixed several days previous to its application. The 
spray materials used in tests (2) and (3) were the same as those 
employed in test (1), except that they had stood mixed about 18 
and 24 hours, respectively, before usage. The chief object of tests 
(2) and (3) was to ascertain whether or not the mixing of these mate- 
rials some time in advance of their use would affect their insecticidal 
value. In test (4) a bucket pump was used for applying the spray, 
a hand atomizer being used in the other three tests. The results of 
this experiment appear in Table XV. 
