24 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE. 



(Parrott, 1900) to six days. Moore's formula is said to protect for 

 two days. This mixture is safe when applied lightly with a brush, 

 but not when applied liberally with a pail spray pump. 



Laurel oil is a very effective repellent. Mayer (1911) found that 

 the protection lasted from 2 to 12 days. The oil when used pure has 

 an irritating effect unless it is applied lightly. According to Mayer 

 the irritating effect may be overcome by combining it with linseed 

 oil in the proportion of 1 to 10. The present author found that 

 10 per cent of laurel oil in cottonseed oil was active for less than a 

 day. 



A number of formulas for repellents for application to wounds 

 have been recommended by various authors. 



In experimental tests carried out by the present author the follow- 

 ing results were obtained : 



A 10 per cent mixture of crude carbolic acid (21.8 per cent 

 phenols) in cottonseed oil has a very strong repellent action on 

 flies, but this lasts less than a day, in consequence of which it is nec- 

 essary to apply the mixture every day. The mixture should be ap- 

 plied lightly with a brush, since a heavy application with a spray 

 pump is likely to cause phenol poisoning. 



Mixtures consisting of 10, 20, and 50 per cent of pine tar in cot- 

 tonseed oil have marked repellent qualities. They should be applied 

 lightly and it is necessary to apply them every day. A liberal ap- 

 plication of a 10 per cent mixture is deleterious to animals. This 

 is also the case with a half-and-half mixture of pine tar and Beau- 

 mont oil when applied lightly with a brush. 



A mixture of oil of tar (14 per cent phenols, volatile with steam) 

 in cottonseed oil and in Beaumont oil has a very marked repellent 

 action. A 10 per cent mixture of oil of tar in cottonseed oil is safe. 

 A half-and-half mixture of oil of tar and cottonseed oil when ap- 

 plied liberally with a spray pump and 50 per cent oil of tar in Beau- 

 mont oil applied with a brush are not safe. Ten per cent oil of tar 

 in Beaumont oil is safe. When applied lightly it is necessary to 

 apply 10 per cent oil of tar in cottonseed oil or 10 per cent oil of tar 

 in Beaumont oil every day. 



Mixtures of 10 per cent of oil of citronella, oil of sassafras, or oil 

 of camphor in cottonseed oil are powerful repellents, but they are 

 active for less than a day. 



A heavy application of fish oil causes the hair to become sticky 

 and fall out. A light application did not produce these results. 



Pyrethrum powder is an effective repellent, but its action lasts 

 only for about a day. 



