356 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



produce diseases in man and other animals. The most im- 

 portant of these are the relapsing fevers of which there are 



FIG. 150. Relapsing fever tick, Ornithodorus moubala. (About four 

 times natural size.) 



FIG. 151. The fowl-tick, Argas persicus. (About four times natural size.) 



several types caused by as many different species of Spiro- 

 chceta. The relapsing fever of Africa, or African tick fever, 



