86 
ments for the purpose of determining the effect of insecticides on the 
insect. The notes I have tabulated below. The results obtained 
from these experiments indicated the lines of attack which were fol- 
lowed out a year later in Curtis Park, Denver. 
Preliminary laboratory experiment in 1903 for determining the effect of different 
insecticides on the cottony maple scale. 
[Treated January 17, 1903; examined January 23, 1903.] 
Insecticide. Strength. | Alive. | Dead. |P oreo Remarks. 
Lime-sulphur-salt (Hl- | Full _..-_....--.--...- 69 67 | 49 
inois formula). | | | 
OD) OMe ee ere a aso QOne*halive So sees 38 | 89 | 70 | 
1D Go ae eae ee Ne | Two-thirds. 2. 26ses 10 | 2A | 71 | 
DO mass oe a a capa ee One:sixthe= === at | BG) | 61 
Kerosene emulsion __-_-_- 50 per cent kerosene_ 10 | 43 | 90 Possibly all dead. 
DD) Ope ne Sone a 25 per cent kerosene- a igh} 92 Those in protected 
| places alive; others 
| dead. 
Dn Re ee eee cee eee 12: per cent kerosene 44 | 67 | 60 | 
Whale-oil soap (hard)-__| 1 pound to 1 gallon __ 12 140 | 92 All dead, except occa- 
| sional protected ones. 
DO eee nes Rees Ee 1 pound to 2 gallons - 53 23 | 30 | 
1D oye 2 Seeeeeaere Spey Os ipound to4 gallons! 22s |-s a [ ere ene aa | Little, or no effect. 
IDO) es ee SOC eee 1 pound to 6 gallons - 12 60 83 | 
CHeCkeEe sel ee) Ae ee a eer eee eS ae 62 5D | 47 
Results of a second experiment in 1903. 
[Treated January 31, 1903; examined February 10, 1903.] 
Insecticide. Strength. | Remarks. 
meoposene emulsion =_22 52 __.-| 50 per cent kerosene _| Seems to have killed all. 
Ree eat eres ee Rh ee | 25 per cent kerosene_| Seems to have killed about all. 
Whale- OUSOR is i ee ee eas ee | 1 pound to 1 gallon __| Seems not to have killed any, but there 
may be different results later. 
Lime-sulphur-salt (Illinois | Full _______._._______- | Seems not to have killed any. 
formula). | | 
It will be seen by consulting the tables that the mortality of the 
untreated scale during the winter reaches probably 50 per cent. 
This is indicated by the counts on the check branches and those on 
which the treatments were so weak as to have had little or no effect. 
‘The numbers counted in the laboratory experiments were too small 
to have positive values except where the percentage of dead was very 
high, because the difference in mortality on different twigs is a 
conspicuous feature on looking over the hibernating insects. 
The only effective remedies appeared to be kerosene emulsion, 25 
per cent or more in strength, and whale-oil soap at the rate of 1 
pound to the gallon. The laboratory experiments indicated that 
further tests with kerosene emulsion, varying in strength from 10 
to 50 per cent, and the stronger solutions of whale-soap should 
be made to ascertain more accurately the location of the “dead line.” 
