128 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



infestation in lambs, especially in the case of the stomach worm, 

 although on the other hand it appeared that a change of pasture 

 every week during the season from May 1 to September 1 kept down 

 the infestation of lambs with hookworms, nodular worms, lungworms, 

 and tapeworms to a very small amount. Seemingly, therefore, these 

 parasites can be more easily controlled than the stomach worm by a 

 system of pasture rotation. 



That the number of stomach worms present in a given animal 

 becomes, under some circumstances at least, greatly diminished dur- 

 ing the winter, is an interesting point brought out in the investiga- 

 tions ; and if this proves to be the rule, and if the controlling circum- 

 stances can be determined, a fact of no small practical importance 

 will have been established. The probable meaning of the presence 

 of only a few stomach worms in sheep during the winter following a 

 summer in which they were comparatively numerous in other sheep 

 of the same flock is that the average length of life of the adult 

 stomach worm is not more than a few weeks or months ; in brief, that 

 the stomach worm is essentially a short-lived parasite. 



In the series of experiments following the foregoing and now in 

 progress, medicinal treatment is being combined with the periodical 

 changing of pastures, inasmuch as it appears that methods based 

 upon the changing of pastures alone are not likely to prove satis- 

 factory in the control of the internal parasites of sheep, particularly 

 in the case of the stomach worm. 



TREATMENT AND CONTROL OF EXTERNAL PARASITES. 



Sheep ticks. — A series of experiments on the treatment of sheep 

 to destroy ticks, extending over about two years, has been completed, 

 and a Farmers' Bulletin on the subject is in course of preparation. 

 Further experiments to check the findings of earlier work are still 

 in progress. Plans are being made for a series of experiments on a 

 very large scale in Wyoming. 



Sheep scab. — A series of experiments which has been in progress 

 about one year is nearing completion. These have to do with the 

 vitality of the scab mite, the curative and protective action of various 

 dips, the value of sulphur as a scab remedy, and various other phases 

 of the sheep-scab problem. 



Spinose ear ticks of cattle. — Experiments in the treatment of cattle 

 to destroy ear ticks have been carried on in New Mexico, California, 

 and Texas. Various substances have been tried as remedies, includ- 

 ing castor oil and nicotin, arsenical solutions, tar oils, carbolic acid, 

 and pine tar, using various methods of application. Varying success 

 has been obtained, but no fully satisfactory remedy has been dis- 

 covered. 



Cattle lice. — Experiments in treatment for cattle lice have been 

 carried on in Colorado, Nebraska, and New Mexico. From the data 

 now at hand it appears, so far as concerns the biting louse and the 

 long-nosed sucking louse, that the lime-sulphur-arsenic dip and the 

 Bureau of Animal Industry arsenical solution will free cattle from 

 lice in a single dipping, whereas coal-tar creosote dips, nicotin-and- 

 sulphur dips, and nicotin dips require two dippings, with an interval 

 of about two weeks between dippings. Lime-sulphur dip is not effi- 



