Investigations into the Nature, Causation, and Prevention of Texas or Southern Cattle Fever Page: 89
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TRANSMISSION OF TEXAS FEVER.
(.0268 inch) in lelgtllh, including the ilontli parts. They move actively
about, carrying in their cloacal opening the chalky mass of urates (?)
mentioned above. They collect along the edge between dish and cover,
and scatter as soon as the cover is removed. When confined for some
time in the dish, this becomes soiled with a large number of white dots
discharged by the ticks.
These minute creatures are very tenacious of life when kept confined
in glass dishes containing a little loam or some leaves. Young ticks
hatched about the middle of December, 1890, were confined in the same
glass dish in the laboratory during the winter. On May 1, 1891, four
and a half months after hatching, they were still active. On May 19
a few were still active; some were inert, but not yet dead. Young ticks
hatched about July 20, 1891, were still active August 29. The para-
sitic habit of the tick is probably so complete that no growth and no
further development takes place unless the larvae gain access to cattle.
When they have once attached themselves to the host and begin to get
nourishment in the form of blood their growth is assured.
We have already referred to the larval and nymphal stage, so-called,
as observed by Curtice. In his observations each stage occupied about
a week, so that at the end of two weeks the female tick is sexually
mature, prepared to become fertilized, swell up and drop off to lay her
eggs as the beginning of another generation. When young ticks
hatched within a few days of one another are placed on cattle they do
not necessarily mature at the same time. The dropping off of ripe
ticks may go on some days before the animal is completely freed. In
general, the time required for the tick to mature and drop off is from
twenty-one to twenty-three days. These figures are the result of nu-
mercus observations made in the experiment fields at the station. The
date being known when the larvae were placed on the cattle, this period
was easily determined.
The life history of the tick after it has attached itself to cattle is thus
easily told. Taking two weeks for the tick to become sexually mature,
the -fertilization takes place as described by Curtice. An examination
of the skin of cattle at this time shows each female provided with a
male. After fertilization the female enlarges very slowly until from
the nineteenth to the twenty-second day, when she swells up very raps
idly, a day or two producing great change in size. When the proper
stage is reached she loosens her hold upon the skin and drops to the
ground, where the laying of eggs begins in a few days. The length of
time elapsing between successive generations of ticks may be tabn-
lated approximately as follows:
From oviposition to the larval stage (period of incubation) .......... 20 to 45 days
From larval to adult state (parasitic stage) ........................... 21 to 23 days
Age of one generation .......................................... 41 to 68 days89
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Smith, Theobold & Kilborne, Fred Lucius. Investigations into the Nature, Causation, and Prevention of Texas or Southern Cattle Fever, book, 1893; Washington D.C.. (https://texashistory.unt.edu/ark:/67531/metapth143538/m1/89/: accessed April 25, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting University of Texas Health Science Center Libraries.