340 INSECTS AFFECTING STOCK AND POULTRY 



or indirectly, but among the Arachnids at least two ticks, in the 

 light of our present knowledge, are now recognized as dangerous. 

 These both inflict loss upon cattle raisers. 



"Texas fever" or "Tick fever" affects southern cattle infested 

 with the species of tick Margaropus annulatus Say. Its ravages 

 are not confined to Texas. The disease is infectious, caused by the 

 transmission into the blood of the animal of a parasitic protozoan 

 existing in the body of the tick. Symptoms of the presence of the 

 disease are high fever, a reddish urine, loss of flesh, and, in a large 

 number of cases, the death of infected cattle. This disease may 

 also occur in northern cattle, brought south and turned out upon 

 the ranges; or northern cattle may become infected from ticks 

 brought north on southern cattle. Specimens of this tick (Fig. 



FIG. 345. North American fever tick; newly moulted nymph on left, adult female just 

 beginning engorgement, and fully engorged female. (After Cotton, Tenn. Bull. 113.) 



345) have been found on dogs frequenting the tick-infected coun- 

 try. The pest has so seriously threatened the cattle industry 

 that the Federal Government has established a quarantine line, 

 imposing severe restrictions on the passage of cattle out of the 

 quarantine zone. In states south of this line the fever tick has 

 cost agricultural interests every year something like one hundred 

 million dollars (Tenn. Bull. 81). 



The Rocky Mountain spotted fever tick (Dermacentor venustis 

 Banks), transmitter of the disease known as Rocky Mountain 

 spotted fever, has been most destructive in the Bitter Root Valley, 

 Montana, but also occurs in Nevada, Idaho, Utah, Wyoming, 

 and possibly other states. When human beings are bitten by this 

 tick eighty per cent of the cases result fatally. 



Life History. Immature ticks of this latter species frequently 

 feed on smaller mammals, such as ground squirrels; the mature 



