CONTROLLING INSECT PESTS 419 



closing the door and cracks of the closet. Or infested cloth- 

 ing may be put into a tight trunk or box together with a small 

 saucer of the liquid. It is highly explosive and must never be 

 used in the presence of any artificial light. 



When sulphur is burned, very poisonous fumes, mostly 

 sulphur dioxide, are given off. This gas is fatal to all animal 

 life and is sometimes used in fumigating rooms or other en- 

 closed spaces that are infested with insects. Under the head 

 of " Clayton gas" it has recently been much used for fumigating 

 ships and ship's cargoes to kill the rats and insects that are so 

 often found in the holds. It is very penetrating and effective 

 but is usually objectionable on account of its strong bleaching 

 properties especially in the presence of moisture. Seeds treated 

 with this gas will not germinate. 



Repellents. There is a popular belief that any ill-smelling 

 substance will keep insects away from plants. While this is 

 not wholly true there are some substances which when applied 

 to a plant seem to afford it more or less immunity from the 

 attacks of certain insects. Bordeaux mixture, crude carbolic 

 acid and thick soap washes are among the most effective of 

 such substances and the various proprietary repellant mixtures 

 that are on the market usually depend on one or more of these 

 substances for their usefulness. As a general rule but little 

 reliance can be placed on them. 



How TO OBTAIN STATE AND GOVERNMENT PUBLICATIONS 



Frequent reference has been made and will be made in the 

 following chapters to various reports or bulletins issued by 

 state officials or by the United States Department of Agricul- 

 ture. Some of these are technical in character and intended 

 for special students but most of them are written for the general 

 public and give in a clear concise manner the results of the 

 latest studies and investigations on the subjects discussed. 



The reports and bulletins of the various State Agricultural 

 Experiment Stations can be had by applying to the director of 

 the station in whatever city this station is situated. When 

 making application for such bulletins the applicant should state 



