TEXAS OR TICK FEVER 189 



Life history. — The methods just given are based on the fol- 

 lowing facts concerning the life history of this tick: the full- 

 grown female tick drops off the cattle when she becomes en- 

 gorged with blood. Her heavy body and small, short legs make 

 crawling difficult, so she gets under the dry grass, or "trash" 

 close at hand. "Within a few days she begins laying eggs, and 

 lays from 1,500 to 2,500 during the next two weeks. In warm 

 weather, under favorable conditions, these eggs hatch in two 

 or three weeks. The period may be prolonged for eight weeks, 

 or indeed, the hatching be prevented entirely, if the weather is 

 sufficiently cold. 



The young ticks are very small when first hatched, being 

 scarcely visible. They crawl up the grass, weeds, or small twigs, 

 and there wait for the cattle to come along. If no cow, mule, 

 or horse comes along for several months, these small ticks die 

 from starvation, for they have no other known means of obtain- 

 ing food for development. If the young ticks succeed in lodg- 

 ing upon the skin of a cow, then in three or four weeks (and in 

 cold weather much longer) they reach their full growth. The 

 females, being engorged with blood, drop off and begin laying 

 eggs as did their mothers. 



Neither old nor young ticks crawl far, hence a fence with a 

 bottom rail or board on the ground will stop them, but wire 

 fences do not always afford protection. 



Ticks do not crawl from one animal to another. 



Eggs laid during the cold weather of late fall and early 

 winter do not hatch, but go through the winter as eggs and hatch 

 when warm weather comes in the spring. 



All eggs laid before September 1 will probably hatch the 

 same fall, and, therefore, the young ticks will be killed by the 

 cold winter weather or starve to death before spring. 



Vaccination. — Not only does tick fever kill hundreds of thou- 

 sands of dollars' worth of Southern cattle every year and depre- 

 ciate the value of all those marketed from one fourth to one half 

 cent per pound live weight, but it also offers the greatest exist- 

 ing barrier to the improvement of the quality of cattle in the 

 tick-infested area by rendering the importation of pure-bred 

 animals for breeding purposes extra hazardous and expensive. 



For the purpose of conferring immunity on imported pure- 

 bred or other cattle, a method of inoculation has been found 

 practicable which very greatly reduces the otherwise heavy loss. 



