Il8 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTUBE, 



meters of 1 per cent copper sulphate solution. Monthly fecal exami- 

 nations have shown that the number of parasites among these year- 

 lings was kept down to a low figure. 



A few wethers born in the spring of 1915 have been kept con- 

 stantly in the stable since birth, and upon monthly fecal examina- 

 tions have never shown more than a few parasite eggs and frequently 

 have shown no eggs at all, indicating their practical freedom from 

 parasitic infestation. Under these conditions their growth has been 

 vigorous and their health excellent. 



It was again observed, as in the year before, that in all the sheep 

 at the Vienna station the number of stomach worms and similar para- 

 sites greatly diminished during the winter, 



TREATMENT AND CONTROL OF EXTERNAL PARASITES. 



Cattle lice. — Sufficient experimental work on cattle lice has been 

 completed to justify publication on this subject, and a manuscript has 

 been prepared for a Farmers' Bulletin. Three species of lice — two 

 sucking and one biting — ^have been found to be of common occurrence 

 on cattle. The greatest losses have been found to occur in young 

 stock and poorly nourished old animals. Dipping has proved the best 

 method of treatment. Two dippings are necessary for eradication in 

 most cases; sometimes more than two are required, especially in the 

 case of the short-nosed cattle louse. The most suitable interval be- 

 tween dippings seems to be 15 or 16 days. Arsenical dips, coal-tar 

 creosote dips, and nicotin solutions have given good results as rem- 

 edies. 



Hog lice. — Various dips were tested in Utah and Colorado as rem- 

 edies for hog lice. In some cases eradication was accomplished by a 

 single dipping, but generally two dippings were required, 15 to 16 

 days being a suitable interval. The following dips were found to be 

 efficacious: Coal-tar creosote, cresylic acid (compound solution of 

 cresol U. S. P., diluted 1 to 100), arsenical dip (low strength, about 

 0.18 per cent arsenic trioxid), nicotin (0.07 per cent), and kerosene 

 emulsion (10 per cent). Under varied conditions it was observed 

 that hog lice survive only three or four days away from their host, so 

 that places in which infested hogs have been kept may be considered 

 practically free from infection within a week after the removal of 

 the hogs, although theoretically there would still remain a possibility 

 of infection from young lice hatching from dislodged eggs. 



Sheep and goat lice. — Experiments in the treatment of sheep and 

 goats for lice have been carried on in Utah, New Mexico, Texas, and 

 California. Some of these experiments were arranged on a small 

 scale; in others large numbers of animals were dipped under practi- 

 cal field conditions. The lice were more difficult to eradicate from 

 animals on the open range than from those confined in pens and 

 fed hay and grain. Sucking lice appeared to cause more injury than 

 biting lice, although sheep and goats grossly infested with lice of 

 any species failed to thrive and the irritation to the skin caused the 

 animals to rub and lose wool. Two dippings were found necessary 

 for eradication, with an interval of 14 to 16 days. Biting lice, how- 

 ever, which appear less difficult to destroy than sucking lice, were 

 frequently eradicated by one dipping. Successful results were ob- 



