124 



PRACTICAL ZOOLOGY 



In this way the disease germs are transmitted from one animal 

 to another. 



The control of the Texas-fever tick is very simple. The adult 

 ticks die after laying their eggs, and the young die if they do not 

 gain access to cattle within a few months. A pasture may thus 

 be freed from ticks if left vacant for a few months (Fig. 68). 

 Ticks may also be removed from cattle by dipping the animals 

 in vats containing substances such as crude petroleum or arseni- 

 cal mixtures which kill the ticks. 



Chicken Mites. Poultry in this country may be attacked by 

 chicken mites and fowl ticks. The mites (Fig. 69, A) are about 



FIG. 69. Arachnida parasitic on domestic animals. 

 A, chicken mite ; B, fowl tick ; C, scab mite. (After Salmon.) 



-^V of an inch long, and red in color when rilled with blood, but 

 at other times gray. They suck the blood of the poultry usually 

 at night and hide in crevices during the daytime. A thorough 

 cleansing of the chicken house and an application of a twenty 

 per cent kerosene emulsion will destroy most of the mites. In 

 many parts of the country the chicken mite is considered the 

 most serious poultry pest. 



Fowl Ticks. The fowl ticks (Fig. 69, B) are also a serious 

 pest in the warmer parts of this country. They resemble the 

 chicken mite in shape, but are almost ^ of an inch in length and 



