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Imes (M.). The Spinose Ear Tick and Methods of Treating Infested 

 Animals. — U.S. DepL Aqric, Washington, D.G., Farmers' Bull. 

 980, May 1918, 8 pp., 4 figs. [Received 24tli March 1919.] 



Ornitliodorus megnini (spinose ear tick) is a parasite especially preva- 

 lent in the semi-arid sections of the south-western United States, where 

 it has become a very important pest. The removal of live-stock 

 from the infested area causes the tick to become widely disseminated, 

 but as moisture is apparently detrimental to it during certain stages 

 in its life-cycle, it does not become established to the same extent 

 in other parts of the United States. It is most frequently found in 

 the ears of cattle, horses, dogs and sheep, and in infested areas wild 

 animals, especially jack rabbits, are often severely attacked. 



The ticks enter the ears of the animal as small seed-ticks or larvae, 

 not easily visible to the naked eye, and attach themselves to the 

 tender skin below the hair line. They begin at once to suck blood 

 and in a week or two are fully engorged and shed their larval skin. 

 The nymphs also attach themselves to the skin lining the ear, where, 

 unless destroyed or accidentally dislodged they remain for from 

 1 to 7 months until fully grown and completely engorged. They then 

 fall from the animal and usually crawl upwards several feet from 

 the ground, secreting themselves in dry protected places such as 

 cracks and crevices in buildings, fences and trees, where transformation 

 into the adult, matmg and oviposition take place. So far as known, 

 the adult never attaches itself to animals nor does it take food, though 

 females which do not find a mate have been known to live more 

 than a year. Oviposition may be intermittent and continue over a 

 period as long as 6 months, the death of the female taking place on 

 its completion. The eggs may hatch as early as 10 days after they 

 are laid and the larvae are shortly ready to attach themselves to 

 any suitable animal with which they come in contact, though they 

 have been known to live nearly 3 months without doing so. 



The most effective remedy is a mixture of pine-tar and cotton-seed 

 oil, 2-3 teaspoonfuls of which should be squirted into the ear with a 

 metal or hard rubber syringe of 2-4 oz. capacity. The ear should 

 be held upright for a few seconds to allow the fluid to settle into the 

 ear canal, and if the ticks are packed in closely and deeply, a probe 

 made of a piece of stiff wire 6-7 ins. long and with a closed loop | 

 inch long and \ inch wide at one end should be inserted to loosen the 

 mass and more oil should be appKed. Thia simple and inexpensive 

 preparation consists of 2 parts by volume of ordinary commercial 

 pine tar (Stockholm tar or Barbados tar) and 1 part by volume of 

 cotton-seed oil, which is added to it and stirred until a smooth fluid 

 is obtained. Cotton-seed oil is a fairly good solvent for ear wax and 

 therefore penetrates well. It kills ticks and being of a sticky con- 

 sistency protects the animals from re-infestation for about 30 days. 

 Kerosene oil, gasoline, various dips and disinfectants, and coal tar, 

 unless well diluted with oil, are liable to injure the delicate inner skin 

 of the ear and set up irritation. If too much of the mixture is injected 

 into the ear it will wet the side of the head and blister on exposure 

 to the sun's rays. 



Unbroken horses and wild cattle are best handled in a chute, in 

 wluch, if closely packed, they will hold themselves without additional 



