32 CLASS ARACHNIDA 



the year. An important fact concerning the transfer of 

 disease is that the protozoa in the diseased animal are taken 

 into the body of the tick, and within the body of this host 

 may enter the eggs, so that young ticks that have never fed 

 upon an animal may serve to introduce the parasite in an 

 individual that has not previously had the disease. 



Elimination of ticks from the cattle and prevention of 

 their attacks therefore become essential factors in the 

 eradication of Texas fever. To accomplish the eradica- 

 tion of the ticks in any given locality it is necessary to 

 rotate animals from one field to another, allowing time for 

 hatching of eggs and dying of the ticks before the field again 

 is used as a pasture for cattle. Working upon this basis, 

 considerable areas in the Southern States are now con- 

 sidered tick-free and the hope is that the quarantine line 

 will be pushed farther and farther south until ultimately' 

 the ticks and associated disease may be completely eradi- 

 cated. Certain districts in Tennessee and North Carolina 

 are now considered tick-free and released from quarantine 

 restrictions. 



The Spotted Fever Tick {Dcrmaccntor venusta). — The 

 spotted fe\er tick has come into great prominence in recent 

 3'ears because of the determination that it serves as the 

 carrier of the much-dreaded spotted fe^•er. This disease 

 has caused many deaths in Montana and adjacent States, 

 and the rate of mortality for individuals attacked is very 

 high, so that its appearance is very much dreaded. 



It has been shown that this disease is carried by this 

 particular species of tick, and in no other way. It differs 

 in habit from the cattle tick in that a number of different 

 hosts may be fed upon at different periods in its de\'elop- 

 ment. Usually the young larvse attach themselves to ground 

 squirrels or smaller mammals and remain upon these from 

 three to five days, after which they drop to the ground. 

 After a resting period of from one to three weeks the skin 

 is moidted and an eight-legged form appears, which in turn 

 attaches itself to some host and feeds for several days, 

 dropping to the ground and developing into the adult 



