PROBLEMS OF SPIDERS, MITES, AND TICKS 167 



The poultry mite Dermanyssus gallincz. This is a vicious- 

 looking creature when seen under a microscope. In color it 

 varies from yellowish white to blood red when fully gorged. 



Its presence is sometimes not suspected, for it is a night 

 worker, and during the day it disappears into cracks, especially 

 in the ceilings. If extremely numerous, adults may be found 

 on the fowl, but generally not even the indications of their 

 punctures are visible and only the condition of the poultry 

 shows their existence. There is danger of this mite being 

 carried to the stable, if near by, and the effect upon horses is 

 sometimes serious. Absolute cleanliness in the henhouse is 

 the price of freedom from this pest. 



The Rocky Mountain spotted-fever tick. Dermacentor ve- 

 nustus. The germs of spotted fever are carried from native 

 wild animals to man by the bite of this tick. The life history 

 of the tick consists of four stages the egg, " seed " or larva, 

 nymph, and adult and occupies from one to three years. 

 Failure to find a host during any of the three active stages 

 results in -death of the tick by starvation, and the discovery 

 that earlier stages are largely dependent on the rodents of 

 the region has resulted in a plan of cooperative effort to ex- 

 terminate rodents and ticks together. Since most of the host 

 species are destructive to agriculture, the work is doubly 

 worth doing. <c Cooperation by all landowners in a district 

 is essential to success of any extensive campaign of rodent 

 destruction." 1 It has also been observed that sheep rid land 

 of this tick, and this suggests that they might prove useful 

 against chiggers and other ticks. 



Cattle tick Margaropus annulatus. The germ of Texas 

 fever is now known to be carried by this tick. The loss to 

 the South as a result of this disease has been estimated by the 



1 Clarence Birdseye, ft Some Common Mammals of Western Montana in 

 Relation to Agriculture and Spotted Fever." Farmer' 's Bulletin No. 484. 

 Washington, 1912. 



