1134 



PATHOGENIC PROTOZOA 



each female. The female tick dies in a few days after the egg-laying 

 has been completed. The eggs soon hatch (after nineteen days in 

 summer to one hundred and eighty-eight in winter) and a small, oval, 

 six-legged larva or seed tick appears, and promptly climbs up on the 

 nearest vegetation, grass, weeds or bushes to lie in wait for a warm- 

 blooded host. Although while on vegetation seed ticks do not take 

 food nor grow, their endurance is great, and during the colder parts 

 of the year they may live for eight months. The next stage begins 

 after the seed tick has found a host, when it sucks blood, increasing 

 in size and soon (five to twelve days) molts and a new form, the eight- 



FIG. 163. THE TEXAS FEVER TICK (Margaropus annulatus). 

 live Medicine and Hygiene.") 



(Rosenau, "Preveri- 



legged nymph, appears. In five to eleven days more a second molt 

 occurs and the tick is then sexually mature and males can be dis- 

 tinguished from females. The female does not move about on the 

 animal, but the male seeks her out, and after fertilization growth goes 

 on rapidly until the engorged female drops to the ground. To sum- 

 marize : On the ground is the engorged female, the eggs and seed ticks ; 

 on the animal is the seed tick, the nymph, the sexually mature adult 

 and finally the engorged female. The infected female tick transmits 

 the babesia to the larvas through the eggs, but does not herself bit 

 nor convey the disease directly to another animal. 



It is evident that the tick may be attacked in the pasture or on 

 the cattle. Pasture rotation is one of the methods recommended by 

 the Agricultural Department, and its rests upon the fact that all the 

 ticks will die from starvation in an unused pasture in from six to 

 twelve months, varying with the climate, the shorter period holding 

 true for warmer localities. By changing pastures a farm may be freed 



