INSECTS AND INSECTICIDES 
4 1 
water and acid have mixed, add the potassium cyanide. A good 
way to add the poison is to have it tied in a paper sack and placed 
upon a piece of board over the dish containing the acid and water, 
with a string attached to the sack and passing to the outside. 
Then, when everything has been made tight, a puli on the string 
will precipitate the sack of cyanide in the acid and a rapid escape 
of the poisonous fumes (HCN) will immediately take place, caus¬ 
ing violent bubbling of the liquid. Filling ones lungs with these 
fumes would cause almost instant death, so great care must be taken 
not to breathe them. Fumigating rooms must be arranged so that 
doors or windows of some sort can be raised from the outside 
quickly. Then a thorough airing must take place before anyone 
enters. 
It would require considerable space to give full directions for 
the fumigation of orchard trees, and, as there is little likelihood that 
such fumigation will be called for in Colorado for some time to 
come, I shall not take space to describe the process here. Those 
specially interested can obtain bulletins giving full directions from 
the Deparnment of Agriculture, Division of Entomology, Washing¬ 
ton, D. C. Full directions can also be obtained in a book entitled 
“Fumigation Methods,” by W. G. Johnson, and published by 
Orange Judd Co., New York. 
SUBSTANCES THAT REPEL. 
There are a number of substances that are more or less useful 
for the purpose of driving insects away from places where they 
would cio harm if unmolested. I give below a few of the most 
important. 
28. NAPTHALINE, GUM-CAMPHOR, AND MOTH BALLS. 
Napthaline crystals are much used in insect boxes and in boxes 
or trunks where furs, feathers or woolen gooods are kept, for the 
purpose of keeping out insects that feed on these animal products. 
It is probably the best single chemical that can be used for this 
purpose. Gum-camphor is also much used for the same purpose 
and moth-balls are a combination of these two volatile substances. 
These materials cannot be used to kill insects, but onlv to repel 
them. 
29. TOBACCO. 
Tobacco, in the form of dust, or otherwise, is often used for 
the same purpose as the preceding, but to be effectual must be used 
quite freely. 
30. ASHES. 
Ashes, particularly from wood, are frequently used to dust 
