TICKS BISHOPP 399 



THE SPINOSE EAR TICK 



The spinose car tick, known scientifically as Omithodoros megnini 

 Dujjes, derives its common name from the spine-covered body of the 

 nymphal stage (see pi. 3, fig. 1) and the fact that it attaches and 

 develops deep in the external ear. This species is a serious pest of 

 cattle and horses in the semiarid portions of the Southwest. It also 

 freely attacks nuiles, goats, sheep, hogs, dogs, cats, and even man. A 

 single tick attached deep in the ear will cause considerable irritation 

 and pain, particularly in the case of man, and when the infestations 

 in livestock become heavy they cause the ears to droop and a general 

 unhealthy condition to become manifest. 



The small six-legged seed ticks are found crawling rapidly about 

 on fence posts, trees, and other objects, and when they are brushed 

 off by a passing animal they soon find their way into the folds at 

 the bottom of the external ear wdiere they attach. The larvae be- 

 come engorged in about a week. In this stage they are peculiar- 

 looking pear-shaped objects, with legs scarcely visible. The molt 

 takes place in the ear, and the spiny nymphal stage attaches in the 

 same region and begins engorgement. They require from about 3 

 weeks to as long as 7 months to become fully engorged. They then 

 detach, fall to the ground, and crawl upward on fence posts or trees 

 where they find protected places, molt their sldns, mate, and begin 

 laying eggs. Unlike any other tick, this species does not feed in 

 the adult stage, there being sufficient nourishment carried forward 

 from the nymphal stage, to produce its quota of about 800 eggs. 

 The egg-laying habit of this species is rather remarkable in that it 

 is very intermittent. Oviposition usually begins within 8 to 15 

 days after the nymphs leave the ear of the host, and small batches 

 of eggs may be deposited from time to time over a period of more 

 than six months. This perhaps is an adaptation of the tick to the 

 hot dry condition of the arid Southwest and doubtless helps to in- 

 sure the perpetuation of the species. 



The best method of destroying the ticks in the ears of livestock 

 is by injecting into the outer ear a mixture of 2 parts of commer- 

 cial pine-tar oil and 1 part of cotton-seed oil. Where the ticks are 

 abundant in the posts of corrals and fences near the congregating 

 places of livestock they may be destroyed by spraying such fences 

 with creosote oil. 



THE RELAPSING FEVER TICK 



The leathery-bodied tick, known scientifically as Omithodoros tur- 

 icata Duges, is related to the two i)receding species. (See pi. 3, fig. 

 2.) It has been definitely connected with the transmission of re- 

 lapsing fever of man, and very likely is tlie most important, if not 



