10 BULLETIN 45, U. S. DEPARTMENT OF AGRICULTURE. 



There would be some very serious objections to using sheep ex- 

 clusively in the destruction of ticks, even though they should be found 

 to Id 11 practically all the ticks which get on them. In the first place, 

 it would be. necessary to eliminate all live stock except this on which 

 the ticks could be destroyed at weekly intervals by dipping or other- 

 wise. Secondly, it is impracticable to stock heavily a given area with 

 sheep and attempt to carry the usual number of other live stock on 

 the same pastures. It would thus be necessary to reduce greatly the 

 number of live stock other than sheep in order to graze a sufficient 

 number of sheep to have any appreciable value as collectors of ticks. 

 Moreover, it would be necessary to cut down all vegetation higher 

 than a sheep's back, for there are many ticks that await a host higher 

 than 2 feet from the ground. It would also be necessary to drive the 

 sheep where the ticks were known to be located, for the sheep nat- 

 urally go where the feed is best. In the locality where the experi- 

 ment with 20 sheep was carried on it was found that there were few 

 ticks where the feed was abundant, but many next to the foothills 

 and in the ravines where the feed was scarce. The character of the 

 country on the western side of the valley in many places is also such 

 that it would not admit of herding sheep. Should sheep run con- 

 tinuously in the wooded and brushy country on the western side of 

 the valley they would wear off the wool, which would make them 

 increasingly more susceptible to tick attack and less profitable to the 

 owners. 



The tendency of the tick to attach in bunches would indicate that 

 in case ticks obtained a start on any animal they would breed on that 

 animal with increasing facility ; for it would be more easy, as the fe- 

 males enlarged, for the males to find them. Since most of the en- 

 gorged females picked from the sheep in the experiment had males 

 beneath them, and all of the females which were removed when well 

 engorged deposited eggs which hatched normally, there* appears to be 

 little likelihood that there would be many females to drop which 

 would not be fertile. 



The possibility that sheep may serve as a reservoir for the virus of 

 spotted fever is a point that should be tested before sheep are used 

 at all in the destruction of ticks. 



It appears, however, that sheep are very good collectors of ticks. 

 Six sheep with heavy wool picked up in 11 days about 72 females 

 and 47 males. Although no comparative experiment has been per- 

 formed, it is the writer's opinion that 6 horses or 6 cattle under the 

 same conditions would not have picked up and retained nearly that 

 number. Therefore in " ticky " country which is favorable to the 

 herding of sheep it would be advantageous to use sheep as collectors 

 of ticks. By clipping the sheep once in 7 days it would seem that 

 much good could be accomplished. To bring about the greatest good 



