i86 



THE ANIMALS AND MAN 



prepare it is to add just water enough to stone- or shell-lime 

 to dry-slack thoroughly; then sift and apply as a powder as 

 soon as possible. 



A method of insect killing which is available for use 

 against either biting or sucking insects but which requires a 

 good deal of special preparation and apparatus is that of 

 fumigating with hydrocyanic gas. By covering the tree 

 with a tent and then p:enerating the gas under it by adding 

 cne ounce of pure potassium cyanide 

 to one ounce of sulphuric acid in 

 three fluid ounces of water, all insect 

 life on the tree will be killed. The 

 quantities of cyanide, acid, and water 

 above given suffice to make gas to fill 

 150 feet of tent space. Hydrocyanic 

 gas is deadly not only to insect but 

 also to every other form of animal life. 

 The vapor of bisulphide of car- 

 bon is a very effective insecticide. 

 The bisulphide of carbon can be 

 bought as a liquid in drug stores and 

 a little of it poured into an open 

 saucer which can be placed in a closed closet, or bin or 

 trunk or even in a tight room. It volatilizes rapidly and the 

 fumes are deadly. As the fumes are heavier than air the 

 saucer should be placed in the upper part of the closet or 

 bin. One dram of the liquid will suffice for each cubic 

 foot of space in the receptacle. The vapor is inflammable 

 and explosive and cannot be used where it can come into 

 contact with fire. This remedy is very convenient and 

 effective for clothes' moths. 



For some kinds of insects simple methods of killing by 

 attracting them to light or to poisoned food can be used. 



Preventive remedies for insects such as the screening of 

 windows, the covering of special plants with netting, or the 



Fig. 92. San Jose scale 

 insect removed from 

 its waxen under cover- 

 ing. (Much enlarged.) 



