SHEEP TICK AND ITK ERADICATION BY DIPPING. 9 



this pest, and if they become heavily infes-ted receive a setback at an 

 important period in their development, thus causing considerable 

 financial loss to the owner. 



SPREAD. 



Although sheep ticks do not seem to possess the instinct of migra- 

 tion to any great extent, nevertheless, once introduced into a flock, 

 they spread rapidly until the entire flock is infested. As range sheep 

 are usually close herded, crowded into corrals, and come into close 

 contact on the bed grounds, the ticks pass readily from one animal 

 to another. On farms, where the sheep are not close herded but 

 graze in fenced inclosures, the conditions are not so favorable to 

 rapid spreading; but during cold weather, when such sheep are 

 placed in corrals, sheds, or barns, in close contact, -every member of 

 the flock as well as the premises will almost certainly become infested 

 if there are ticks on any of the sheep. 



While sheep ticks will not propagate or even live for any consid- 

 erable time on other animals than sheep,^ they may be harbored 

 temporarily by dogs or other animals which have come in close con- 

 tact with an infested herd. Men working among infested sheep may 

 cany the parasites on their clothing and thus be the means of intro- 

 ducing them into clean flocks. If separated from the sheep the 

 ticks do not live longer than about 4 days, as a rule, and it might 

 be assumed that plnces from which all sheep had been removed 

 would become free from sheep ticks within a very few days. How- 

 ever, the survival of dislodged ticks is not the only factor influencing 

 the length of time premises may remain infested after the removal 

 of infested sheep. Tags of wool to which pupae are attached may 

 be pulled out by bushes, fences, etc., or by the sheep themselves. 

 If the weather is warm and other conditions favorable these pupae 

 will hatch and infest the premises. 



Under ordinary conditions the period of incubation is from 19 to 

 24 days and in some cases longer, the length of the period being 

 influenced by temperature and other factors. Laboratory experi- 

 ments have indicated that the incubation period of pupae removed 

 from sheep may be as long as 46 days. Infested sheep, in their 

 efforts to obtain relief from the irritation and itching, may 

 dislodge some of the ticks and eggs. The ticks will die in a few 

 days, but if conditions are favorable the pupae or eggs will retain 

 their vitality and hatch in due time. The pupae dislodged from the 

 sheep during cold weather or when the nights are frosty will not 



1 Experimental data seem to Indicate that sheep ticks may live and propagate on goats. 

 Dr. E. R. McClure placed 12 ticks on an Angora goat and held the goat under observa- 

 tion for 60 days. The ticks lived and propagated during this period, at the end of 

 which time the goat was returned to the flock and observations were discontinued. 

 75592°~Bull. 798—17 2 



