e readily understood when we recall the life history of ticks.
The southern cattle leave only matured ticks which have dropped from them.
These must lay their eggs and the latter must be hatched before any ticks
can get upon native cattle. The shortest period is thus not less than 30
days if we include 10 days for the period of incubation after the young
ticks have attached themselves to native cattle. When the infection of
pastures with ticks has taken place 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 already 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 they prefer--the thighs, escutcheon,
and udder. After the acute stage of the fever has passed the ticks begin to
swell up and show very plainly. (Pl. XLVI, figs. 6 and 7.)

_Prevention._--It is generally accepted that if southern cattle are
entirely free from that species of tick known as _Margaropus annulatus_
they can be allowed to mingle with the most susceptible animals without
danger. Furthermore, it has been learned from the study of the life history
of the cattle tick and by observation 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 view
should be directed toward the destruction of ticks on cattle as well as
their eradication from the pastures.

METHODS OF ERADICATING THE TICKS.[7]

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 followe