TEXAS PEVEE. 485 



early in the season, or when it is cold, the period is much longer, 

 because it takes longer for the eggs to hatch. 



If native cattle are placed upon pastures which have been infected 

 with ticks some time before, the disease will appear so much sooner, 

 because the young ticks may be ali-eady hatched and attack the cattle 

 at once. It will be evident, therefore, that the length of time between 

 the exposure of native cattle on infected fields and the appearance 

 of the disease depends on the date of original infection, and on the 

 weather, whether cold or hot. When native cattle are placed upon 

 fields on which young ticks are already present, they will show the 

 fever in 13 to 15 days if the season is hot. 



The fever appears before the ticks have matured. In fact, they are 

 still small enough to be overlooked. In any case very careful search 

 should be made for them in those places which thej' prefer — the 

 thighs, escutcheon, and udder. After the acute stage of the fe^'er has 

 passed the ticks begin to swell up and show very plainly. (PI. XL VI, 

 figs. 6 and 7.) 



Prevention. — It is generally accepted that if southern cattle are 

 entii'ely free from that species of tick known as Margdropus annu- 

 latus they can be allowed to mingle with the most susceptible animals 

 without clanger. Furthermore, it has been learned from the study 

 of the life history of the cattle tick and from that fact that this tick 

 infests pastures only transiently, never permanently, and will not 

 mature except upon cattle or equines, that its extermination is 

 possible, and that the disease it causes may be prevented. Therefore 

 the various methods with these results in v'iew should be directed 

 toward the destruction of ticks on cattle as Avell as their eradication 

 from the pastures. 



The details of these methods of eradication will not be discussed 

 here, as this subject is fully treated in Farmers' Bulletin 498, 

 " Methods of Exterminating the Texas-fever Tick," which may be 

 obtained free upon application to the Department of Agriculture, 

 Washington, D. C. 



METHODS OF ERADICATING THE TICKS. 



In undertaking measures for eradicating the tick it is evident that 

 the pest may be attacked in two locations, namely, on the pasture 

 and on the cattle. 



In freeing pastures the method followed may be either a direct or 

 an indirect one. The former consists in excluding all cattle, horses, 

 and mules from pastures until all the ticks have died from starvation. 

 The latter consists in permitting the cattle and other animals to con- 

 tinue on the infested pasture and treating them at regular intervals 

 with agents destructive to ticks and thus preventing engorged females 

 from dropping and reinfesting the pasture. The lar^•a3 on the pas- 



