336 SANITARY ENTOMOLOGY 



swers for this spraying. Thoroughness is essential and it is sometimes 

 necessary for two or three to work on the same animal at the same time 

 brushing the spray material into the hair before it runs off. 



Some dairymen do not take measures against the lice on their cows 

 because they feel that spraying is the only method that will reach 

 these insects, and that the danger from the animals catching cold after 

 such a treatment more than offsets the injury of the lice. There is but 

 little danger of cows catching cold if they are in good health, particu- 

 larly if the day is not too cold, and if the cows are covered well after 

 the treatment. 



Our trials indicate that the average spraying material such as creo- 

 lin, kerosene emulsion, or an arsenical wash, together with the labor fac- 

 tor, costs about ten cents per animal for each treatment. 



There are disadvantages in this treatment, including the labor and 

 time factors : the amount of equipment necessary ; and the fact that a 

 number of these sprays are not effective enough to kill the lice, or they 

 are too strong for the cow's skin, or their effectiveness does not last for 

 any considerable time after the application. The most important of 

 these control measures are listed and their advantages and disadvantages 

 mentioned. 



Creolin. — Of the materials used for spraying cows a solution of creo- 

 lin is one of the most common. The strength should not be less than four 

 per cent to kill the lice, and not more than five per cent, as this will cause 

 some scurfing. A four and one-half per cent solution will give the best 

 results for creolin. 



Kerosene Emulsion. — This emulsion has been used with satisfactory 

 results by some dairymen. It is made by shaving one-half pound of 

 laundry soap in one gallon of soft water that has previously been 

 brought to the boiling point. When the soap is all dissolved, remove 

 from the fire and add two gallons of kerosene oil. Stir this thoroughly, 

 and if you have a bucket pump, place this in the mixture, turning the 

 nozzle back into the bucket so the material is constantly passing through 

 the pump. This will form a cream emulsion. If any free oil separates 

 from this mixture continue pumping until the oil ceases to show. Then 

 mix this amount with twenty gallons of water and apply either with a 

 spray pump or with a brush, preferably the former. In using kerosene 

 emulsion we have observed that the lice were not killed with a mixture 

 that was so weak that it would not do injury to the skin of the 

 animals to which it was applied. For this reason the linseed oil gives much 

 better results. 



Arsenical Washes. — Arsenical washes are also used for the control of 

 cattle lice, but owing to the great care necessary in using them, both from 

 the danger of poisoning and the possible injury that may occur by using 



