488 DISEASES OF CATTLE. 



ticks resulting from eggs laid by females that have dropped), the 

 herd is then changed to a second tick-free inclosure for 20 days 

 longer, and if they are not free of ticks by that time they are placed 

 in a third tick-free inclosure for 20 days more. Should the two 

 changes after intervals of 20 days have been made, 60 days will have 

 elapsed, which is ample time for all ticks to have dropped during 

 the portion of the year indicated, and the animals are then ready 

 to be placed on a tick-free pasture or field without danger of be- 

 coming reinfested. The periods to free cattle (given in the above 

 table) are believed to be ample. It will, however, be a wise precau- 

 tion to make a careful examination of the cattle for ticks before 

 placing them in the noninfested field they are to occupy. 



During the part of the year fi'om October to February, inclusive, 

 the tinii- required for seed ticks to appear after females ha^'e dropped 

 is much longer than the time necessary for all the ticks to drop from 

 cattle; consequently, if it is desired, the herd may be continued on 

 the same field for the required length of time without danger of 

 becoming reinfested. 



Freeing ioth cattle and pcustures of ticks hy the rotation method. — 

 The particular scheme of rotation to be followed on a farm depends 

 much on the conditions which have to be met. In figures 1 to -f four 

 plans of rotation are represented. In these diagrams no attempt, 

 except in a very rough way, has been made to indicate the relative 

 size of the fields, as this depends on the number of cattle and on 

 various conditions of a more or less local nature. It rests with the 

 farmer to select his fields with regard to location and size so as to 

 carry out properlj^ and successfully the plan which he adopts. 



The matter of the dissemination of ticks deserves particular atten- 

 tion in considering rotation methods. The engorged females which 

 drop on a pasture will crawl at most only a few feet. The same may 

 be said of the larvas or seed ticks. It is possible, however, for seed 

 ticks to be passively carried considerable distances at times. Dogs, 

 cats, and other animals which ordinarily pass unhindered over farms 

 may become covered with seed ticks while going through one field, 

 and later some of them may be brushed off the animal while passing 

 through the herbage of an adjoining field. Even though the danger 

 of ticks being spread in this manner is not great, it will be well, when 

 practicable, to take precautions against it. 



Again, engorged females, eggs, and seed ticks may be carried by 

 running water from a pasture without injury in any wav. The dan- 

 ger from this source is probably greatest where there are ruanv small 

 streams subject to frequent floods of short duration and on hillsides 

 where the water runs off" with great force during heavy rains. This 

 will, no doubt, in some localities i)resent a rather serious problem in 

 tick eradication. 



