THE CONTROL OF INJURIOUS INSECTS 393 



that the cattle enter one end of a vat filled with warm dip through 

 which they swim, and leave the vat at the opposite end. The lime- 

 sulphur dip is made by niixing 12 lb. unslaked lime and 24 lb. 

 flowers of sulphur in 100 gal. of water. Nicotine dips should con- 

 tain about ^ioo of i per cent, of nicotine, and should be used 

 warm, not above ioo°F. 



2. Spraying the animals. This method is neither so economical 

 nor so effective as dipping, but is recommended where but a few 

 animals are to be treated. 



Cattle lice can be controlled by the following means: 



1. Hand applications with a brush or cloth at intervals of about 

 3 weeks, of (a) cottonseed oil and kerosene (equal parts); (b) kero- 

 sene and lard (>^ pt. to i lb.); (c) crude petroleum; (d) any of the 

 dip solutions. 



2. Spraying with any of the dip solutions. 



3. Dipping in (a), an arsenical solution, prepared as follows: 



4 lb. caustic soda (85 per cent. pure). 



8 lb. white arsenic (99 per cent, pure) in fine powder. 



8 lb. sal soda crystals. 



I gal. pine tar. 



500 gal. water (temp. 65°-9o°F.). 



(b) Coal-tar creosote, sold under many trade names and to 

 be used according to instructions. 



(c) Nicotine solution, sold under many trade names and to 



be used according to instructions. 



(Consult Farmers' Bull. 909 and 1017, U. S. Dep. Agric.) 



3. The Use of Poisonous Gases 



The more important poisonous gases used to control insects are: 

 (a) carbon bisulphide; (b) hydrocyanic acid gas; (c) sulphur dioxide; 

 (d) tobacco; (e) formalin; (/") carbon tetrachloride. 



(a) Carbon Bisulphide. — This is an ill-smelling liquid which is 

 readily volatile. The gas is much heavier than air, and if placed in 

 shallow pans above or on top of grain or other vegetable foods the 

 fumes sink, and being poisonous will kill the insects. It is specially 

 valuable for the fumigation of peas infested with weevils, or grain 



