496 DISEASES OF CATTLE. 



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 ready to be placed on a tick-fi'ee pasture or field 

 without danger of becoming reinfested. The periods to free cattle 

 (given in the above table) are believed to be ample. It will, however, 

 be a wise precaution 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 from October to Januaiy, inclusive, 

 the time required for seed ticks to appear after females have 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 hoth cattU uiul paiftures of ticks hy the rotation nietJu^d. — 

 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 4 

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

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

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

 various conditions of a moi-e or less local nature. It rests with the 

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

 carry out properly 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 larvse 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 these may be bnished 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 being injured in any way. 

 The danger from this source is probably greatest where there are 

 many 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 present a rather serious 

 problem in tick eradication. 



Ticks may crawl from the edge of one pasture into an adjoining 

 pasture, or engorged females may drop from the heads of animals 

 reaching through a di\'iding fence. These difficulties are best over- 

 come by consti-ucting a double fence with an intervening space of 15 

 feet. Such a double fence, if the land does not slope greatly, will 



