212 SCHOOL ENTOMOLOGY 



ture and moisture conditions. The young seed ticks crawl 

 around on grass, weeds, etc., waiting for a chance to attach 

 themselves to an animal; failing in which they die. They 

 are, however, exceedingly resistant and may live for three 

 or four months in summer or from September to April in an 

 open winter. When cattle are found they attach them- 

 selves to the soft skin inside the thighs or flanks, and on 

 other tender and protected parts of the body. They obtain 

 their nourishment by sucking the blood and though so small 

 as to be scarcely visible, may transmit the fever at this stage. 

 The complete life cycle requires from six to ten weeks in 

 warm weather and much longer during the cold seasons. 

 The fever is caused by a small protozoan organism which 

 lives in the red blood corpuscles of the affected animal, 

 breaking them down and causing a high fever. These mi- 

 croscopic organisms are transmitted by the female ticks 

 through their eggs to the young ticks, which then infect the 

 cattle to which they become attached. 



The ticks may be eradicated (see 36), either from the 

 pastures or from the cattle. Possibly the greatest advances 

 in tick-eradication have been made in recent years by means 

 of cleaning the pastures of them. Pastures may be freed by 

 excluding all cattle, horses, and mules until the young ticks 

 have died of starvation, or the animals may be left on the 

 pasture and then treated at regular intervals so as to de- 

 stroy the ticks and thus prevent the engorged females from 

 dropping to the ground and reinfesting the pastures. Ticks 

 which get on the animals will be destroyed by the treatment 

 and those which fail to do so will die in the pasture. On the 

 other hand, animals may be freed from ticks by treating 

 them with a substance which will destroy the ticks or they 

 may be rotated on fields free from ticks until all the ticks 

 have dropped. The methods of rotating pastures and the 



