orms should be caught and thrown. Chloroform is then poured into the
wound, taking care that it penetrates thoroughly into all the burrows of
the screw worm, if necessary using a slender stick or a small bunch of
twisted hay as a probe. The animal should be held for several minutes in
order to insure the continued action of chloroform. Instead of chloroform,
gasoline may be used, and carbon tetrachlorid is said by some authorities
to give good results. Finally, the dead or dying maggots may be removed
with forceps, the wound washed with a weak carbolic or cresylic acid
solution, and painted with pine tar to reduce the chances of further attack
by flies. Finally the wound should be dressed with a carbolic or cresylic
ointment to promote healing and thus prevent further infection, or the
wound may be painted with pine tar. Dipping in the arsenical dips used for
destroying cattle ticks is a convenient method of treatment if many animals
are involved.

[Illustration: FIG. 4.--Screw worm (larva of _Chrysomyia
macellaria_). Enlarged. (From Bureau of Entomology.)]

[Illustration: FIG. 5.--Screw-worm fly (_Chrysomyia macellaria_).
Enlarged. (From Bureau of Entomology.)]

GRUBS, WARBLES, BOTS.

Ox warbles are whitish or, when full grown, dark-colored grubs or maggots
that develop from the eggs deposited on the hairs of cattle by certain
flies known as warble flies. In the United States there are two species of
ox-warble flies, technically known as _Hypoderma lineatum_ and _Hypoderma
bovis._ These flies somewhat resemble bees in their general appearance, but
like all flies have only two wings.

The first named, _H. lineatum_, is commonly called the heel fly and is more
generally distributed over the United States than the other species. The
tail has a distinctive reddish-orange color and the legs are rough and
hairy. This fly commonly deposits its eggs about the coronet, whence the
name of heel fly, and on the fetlocks, knees, and hocks. When cattle are
resting, eggs are deposited along the line of contact of the body with the
soil. Cattle are frequently indifferent to the activity of this fly in
depositing its eggs. Commonly 8 to 10 eggs, sometimes as many as 14, are
attached to a single hair.

In the United States the other warble fly, _H. bovis_, has been found only
in the North (New England, New York, Pennsylvania, Maryland, Michigan,
Iowa, Missouri, and Washington) and has not yet been found in the Southern
S