tates. The most common and most important is the species known as
_Margaropus annulatus_, which transmits Texas fever. Information concerning
this tick and Texas fever has been given elsewhere in this volume (p. 475).

The spinose ear tick (_Ornithodoros megnini_) is frequently found in the
ears of cattle in the western part of the United States, and is of common
occurrence also in the ears of horses, dogs, cats, etc.

When its parasitic stage of development is completed the ear tick leaves
its host. Mating between the sexes occurs after the ticks have cast their
skins following the abandonment of their host. They usually crawl up some
distance from the ground and secrete themselves in cracks and crevices in
trees, walls of buildings, etc., where the females deposit their eggs.

After the eggs hatch, the larval ticks, which emerge from them, when they
succeed in finding a host, enter the ears and gradually develop to the
stage at which they are ready to leave the host animal. The females may
live several months, or even years, if they do not find mates. After mating
they may deposit their eggs intermittently. Hatching of the eggs may occur
as early as 10 days after deposition. The larvae may live for 80 days
without a host. The parasitic period has been observed to vary from about
two to about seven months.

_Treatment._--On account of their habits and great vitality and their
occurrence in various kinds of animals besides cattle, complete eradication
is a difficult problem. The only effective treatment known is to introduce
directly into the ear passages a remedy that will kill the ticks. Later, of
course, the cattle may become reinfested from exposure to infested ranges
or inclosures. The following mixture, however, in addition to killing the
ticks in the ears, will protect against reinfestation for about 30 days:
Ordinary commercial pine tar, two parts; cottonseed oil, one part--in each
case by volume. Animals to be treated are confined in a chute, and the
mixture is injected into the ears with a syringe, after the wax and other
debris in the ears have been cleaned out with a wire probe that has an
eyelet at one end. Further information concerning ear ticks and the details
of their treatment is given in Farmers' Bulletin 980.

BLOODSUCKERS OR LEECHES.

These worms are sometimes taken up by cattle when drinking from ponds. They
may attach themselves to the inner surface of the mouth or nose, and
sometimes reach