ANIMAL PARASITES OP CATTLE. 523 



the root of the tail and if not treated may persist for years. The 

 treatment is the same as for psoroptic mange. 



SARCOPTIC MANGE. 



Sarcoptie. mange is caused by a mite very similar to that which 

 causes itch in human beings. It commonly affects the head and neck, 

 but may also occur on various other parts of the body. Bulls ai'e 

 particularly liable to be affected with this form of mange. Cattle 

 may become infected not only from other cattle, but also from horses, 

 goats, dogs, sheep, and hogs. 



The treatment is the same as for psoroptic mange. 



DEMODECTIC MANGE. 



Demodectic mange, which is caused by a small parasite that lives 

 m the hair follicles, causing pustules, especially on the neck and 

 shoulders, occurs occasionally among cattle in this country and is of 

 importance on account of the injury to the hide. Wlien tanned, hides 

 infested by this parasite are pitted, the pits, in some cases, being 

 so deep that they form holes. No practicable treatment is laiown 

 for this disease. 



TICKS.' 



About 10 species of ticks have been reported as parasites of cattle 

 in the United States. The most common and most imjioitant is 

 the species known as Margarofus amiidatus, which transmits Texas 

 fever. Information concerning this tick and Texas fever has been 

 given elsewhere in this volume (p. 473). 



The spinose ear tick (Oiobius megnird or Ornithodoros megnim) 

 is frequently found in the ears of cattle in the western part of the 

 United States, and is of common occurrence also in the ears of horses, 

 dogs, cats, etc. 



Wlien its parasitic stage of development is completed the ear tick 

 leaves its host. Mating between the sexes occurs after the ticks ha\'e 

 cast their skins following the abandonment of their host. They 

 usually crawl up some distance from the ground and secrete them- 

 selves in cracks and crevices in trees, walls of buildings, etc., where 

 the females deposit their eggs. 



After the eggs hatch, the larval ticks, which emei'ge from them, 

 when they succeed in finding a host, enter the ears and gradually 

 develop to the stage at which they are ready to leave the host animah 

 The females may live several months, or even years, if they do not 

 find mates. After mating they may deposit their eggs intermit- 



1 For a more complete discnssion con.'inlt Farmers' Bulletins riGf) and 4f)R, Bulletins 

 1.30 and iri2 of the Bureau of Animal Industry, and Bulletins 15, teclinicnl series, 72 

 and 106 of tbe Bureau of Entomology, all issued Ijy tlie United States Department of 

 Agriculture, 



