, when its development is complete, it finally escapes. The
anterior end of the grub is at the bottom of the tumor, where the mucus
collects upon which it feeds. By spring or early summer the grub is full
grown and forces its way out of the skin, falling to the ground, into which
it burrows for a short distance and transforms into the pupal stage. In
about a month the mature fly emerges.

It has lately been discovered that a second species of warble fly
(_Hypoderma bovis_) common in Europe is of not uncommon occurrence in
Canada and the northern part of the United States, whereas it was formerly
supposed that the ox warbles of this country were all of the one kind. The
general appearance, life history, and effects of the European species are
much the same as those of the American form.

Grubs weaken cattle, cause them to fall off in flesh and milk, and decrease
the value of the hide. The beef in the immediate vicinity of a grub becomes
slimy and of a greenish color, and is known to the butchers as "licked
beef."

The total loss to this country on account of the warble fly is estimated at
$35,000,000 to $50,000,000 a year, at the least, and may amount to
considerably more.

_Treatment for warbles._--During the winter and spring examine the cattle
for the presence of warbles. By passing the hand over the backs of the
animals the swellings marking the location of the grubs may be readily
found. Pressure properly applied to the swellings will cause the grubs to
"pop out" if they have reached a late stage of development. They may be
more easily removed by means of slender forceps inserted into the opening
of the warbles, and a still more certain method of removing them,
particularly if the lumps are still very small, is to cut into the
swellings with a sharp knife or bistoury, after which they may be pressed
out. Care should be taken to crush all grubs removed, so as to prevent the
possibility of their further development and transformation into flies. In
order that none may escape it is advisable to examine the cattle every two
weeks during the late winter and spring, at each examination removing the
grubs which have developed sufficiently to cause perceptible swellings.

Another method of treatment is to force grease or oil into the openings of
the warbles, which kills the grubs. This method is less certain than that
of removing the grubs, and has the further objection that the dead grubs
remain beneath the skin.

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