. The animans and man; an elementary textbook of zoology and human physiology. ed finelyin one gallon of boiling water. Addthis to two gallons of kerosene audchurn the mixture with a force pumpfor a few minutes until it becomesa soft butter-like mass. This stockemulsion should be mixed with waterwhenever it is desired to make up the (Much enlarsed-)spray, in the proportion of one part of stock to ten parts ofwater. Other insecticides that kill by contact are mixtures ofwhale oil soap and water in the proportion of about onepound of whale oil to six gallons of water; also pyrethrumpowder and wa
. The animans and man; an elementary textbook of zoology and human physiology. ed finelyin one gallon of boiling water. Addthis to two gallons of kerosene audchurn the mixture with a force pumpfor a few minutes until it becomesa soft butter-like mass. This stockemulsion should be mixed with waterwhenever it is desired to make up the (Much enlarsed-)spray, in the proportion of one part of stock to ten parts ofwater. Other insecticides that kill by contact are mixtures ofwhale oil soap and water in the proportion of about onepound of whale oil to six gallons of water; also pyrethrumpowder and water in the proportion of one pound of powderto thirty gallons of water. For scale insects, which are so covered and protected bytheir waxen shell as to be very difficult to kill by contact,washes made of unslacked lime 50 Ibs., sulphur 25 Ibs., salt18 Ibs., and water sufficient to make 100 gallons; or resin20 Ibs., caustic soda (70% strength) 5 Ibs., fish oil 3 Ibs., andwater sufficient to make 100 gallons, may be used. Lime alone is a very good insecticide; the best way to. FIG. 91. A San Josescale insect underneathits waxen covering. i86 THE ANIMALS AND MAN prepare it is to add just water enough to stone- or shell-limeto dry-slack thoroughly; then sift and apply as a powder assoon as possible. A method of insect killing which is available for useagainst either biting or sucking insects but which requires agood deal of special preparation and apparatus is that offumigating with hydrocyanic gas. By covering the treewith a tent and ther generating the gas under it by adding .ne ounce of pure potassium cyanideto one ounce of sulphuric acid inthree fluid ounces of water, all insectlife on the tree will be killed. Thequantities of cyanide, acid, and waterabove given suffice to make gas to fill150 feet of tent space. Hydrocyanicgas is deadly not only to insect butalso to every other form of animal vapor of bisulphide of car-FIG. 92. San Jose scale bon is a very effective in
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