REPORT OF THE ENTOMOLOGIST. 143 
REPORT ON EXPERIMENTS AGAINST SCALE-INSECTS. 
By ALBERT KOEBELE, Special Agent, 
LETTER OF SUBMITTAL. 
ALAMEDA, CaAL., December 26, 1887. 
Sik: I herewith submit report of continued experiments with kerosene emulsion 
and resin «ompound upon various scales, plant-lice, etc., made at Alameda during 
1887, according to your instructions. 
Very respectfully, 
Prof. C. V. RILEY, 
U. S. Entomologist. 
ALBERT KOEBELE. 
THE VALUE OF ARSENIC AS AN ADDITION TO THE KEROSENE EMUL- 
SION. 
Tn the main I followed your suggestion while here in April Jast, in preparing the 
kerosene emulsion, viz, to emulsify with resin compound, and use arsenic acid in 
addition. Iam glad that your hopes in this wash are verified. In every instance 
where your proposed arsenic acid was added either to emulsified kerosene or resin 
compound there has been a complete extermination of the scales. 
At first too much of the arsenic acid was used, resulting inmore or less injury to 
trees treated, particularly so in weak washes. 
The best resulis in preparing the emulsion were obtained by taking 1 part of 
the kerosene to 1 part of lukewarm resin compound. Thus I obtained 2 gallons 
of emulsion in less than three minutes that did not show any trace of separation 
before the end of twenty-four hours. The result would have been not quite so 
good if the resin compound had been used hot in emulsifying, and still less so if 
2 parts of kerosene h d been used to 1 of resin compound; but still this last 
will make a very good emulsion if prepared ‘properly, which is easily done. It has 
the good quality of spreading instantly over the leaves if sprayed with diluent, as 
well as do soap washes. None of the experiments made during dry weather with 
this emulsion alone, i. e., without the additional arsenic acid, were appreciably 
effective. The evaporation was very rapid and in ten minutes after application no 
trace of the wash could be seen. 
In addition I include results of various experiments with resin compound, espec- 
ially upon Aphid, which it affects admirably; and, at the same time, a wash can 
be prepared which will destroy all Aphids and not injure the larvee of Syrphus flies 
nor prevent the parasites from hatching from the infegted Aphids. 
Experiment 158.*—Pure kerosene. 
Pure kerosene on Aspidiotus rapax on Pear. Applied with rag February 22, on 
small and sickly tree, with only one living branch. February 27 a heavy shower 
washed off a number of scales which were loosening. May 5, all the dormant buds 
starting out, trees growing vigorously ; not a living scale could be found. 
Experiment 165.—Kerosene emulsion. 
Prepared of half Inkewarm resin compound} and half kerosene; worked far two 
minutes with pump. This formed agood emulsion. In twenty-four hours oil began 
to appear on top, and on the fifth day three-eights of an inch of oil had collected 
on top, in bottle with 4 inches of emulsion reserved. 
Emulsion, 1 part; water, 10 parts. Applied July 27, on Aspidiotus rapax on Pear. 
Cloudy day and a little rain the following night. Examined August 1 and 19; no 
appreciable result; only small part of young scales were destroyed; new scales form- 
ing numerously. 
*The numbering of these experiments is consecutive with the series published in 
the annual report for 1886, pp. 560 to 572. 
+ Dissolve 8 pounds of sal soda and 4 pounds of resin in 3 pints of water above 
fire; when properly dissolved add water slowly, while boiling, to make 36 pints 
of compound, 
