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1.065 dehyd wed andAM
screw v O= infeqaticin'
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and anyeggs on or ar'Wtid ihO WbpftJ
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'When -woun4s, are difficult to trp
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during the winteri that aftAr UW.9**."
liefore Apral so that thcwdup
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Ill'young d MOM,
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I st. In Florida n4 w temas Ais
to nlidwin .
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of the ear,'especiaffy d sheeip. if
light a .pjication of',pine-
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Erxdi mtioji of, the'screw.voft.,
INFORMATION ON SCREW WORMS
NOT CONTAINED IN THIS PAPER MAY BE
SECURED FROM THE FOLLOWING
U. S. DEPARTMENT OF AGRICULTURE,
WASHINGTON, D. C.
BUREAU of ENTOMOLOGY
and PLANT QUARANTINE
SCREW WORM CONTROL
Bureau of Entomology and Plant Quarantine,
U. S. Department of Agriculture, Division of Insects
Affecting Man and Animals.
W. E. DoVE, Director,
Screw Worm Educational and Control Program,
402 Glenn Building, Atlanta, Georgia
R. A. ROBERTS, Supervisor for Georgia,
P. 0. Box 497, Tifton, Georgia
T. F. MCGEHEE, Supervisor for Alabama,
515 Dexter Avenue, Montgomery, Alabama
W. G. BRUCE, Supervisor for Florida,
P. 0. Box 178, Gainesville, Florida
D. C. PARMAN, Supervisor for Mississippi and Louisiana,
P. 0. Box 1190, Hattiesburg, Mississippi
H. M. BRUNDRETT, Supervisor for Texas,
P. 0. Box 2292, Beaumont, Texas
W. H. CLARKE, Supervisor for South Carolina,
Walterboro, South Carolina
or from the Screw Worm Control Committees of
South Carolina, Georgia, Florida, Alabama, Mississippi,
Louisiana and Texas
THE TRUE SCREW WORM FLY
(Cochliomyia americana), Cush. & Patt.
SCREW WORM CONTROL
Screw worm control depends upon a proper
understanding of (1) how screw worm flies develop,
(2) how to recognize screw worm cases, (3) how to
treat screw-worm infested wounds, and (4) how to
prevent screw worm flies.
The true screw worm lives only upon the healthy
flesh of animals and it is this maggot which causes
most of the damage to livestock. Several kinds of
maggots may be found in wounds and, strange as it
may seem, some are actually beneficial to the animal
by eating away dead and diseased flesh, or by destroying
HOW SCREW WORM FLIES
The screw worm maggot is the young of a
certain kind of fly. A picture of the fly which produces
these worms is shown on the opposite page. It is called
the true screw worm because it is the harmful species.
It is usually the first one to lay its eggs upon the broken
skin of an animal. This injury may be a cut, scratch,
tick bite, or a wound of any kind. The true screw worm
fly does not develop in decaying meat, but many people
M. S. YEOMANS, State Entomologist for Georgia, kindly furnished color plates of the
screw worm fly.
think so because large numbers of flies which look like
the true screw worm fly can be found feeding and
laying eggs on dead animals.
The true screw worm fly breeds only in living
animals. Eggs are laid on the wound and young maggots
begin to appear in 10 to 12 hours. They immediately
bore their way into the flesh and feed in clusters so as
to form pockets in the wounds. More and more flies
come to lay their eggs until finally there are large
numbers of worms eating into the flesh. Unless the
animal is found and the destructive maggots are killed,
it may die in a very short time. If the maggots are not
killed, they become fully grown in 4 to 6 days and drop
out of the wound to the ground where they change into
flies about 10 to 14 days later. The flies then mate and
the females are ready to lay eggs in 7 to 10 days.
HOW TO RECOGNIZE SCREW
When screw worms are present in a wound, there
is a bloody discharge and a characteristic odor. For all
practical purposes, a bloody discharge is sufficient
evidence to identify their presence. A hard swelling
usually accompanies a screw worm infestation. Bloody
frothing from the mouth sometimes indicates that the
lips or gums of the animal are infested. Common blow-
fly maggots do not cause bleeding in wounds.
Animals very often become weak and thin because
of screw worm attack and they stray away from the
herd. Infested sheep and goats hide themselves in under-
brush, trying to keep away from the flies. This habit
makes it hard to find infested animals in time for early
HOW TO TREAT SCREW-WORM
Use only benzol and pine-tar oil. These are the
only materials recommended by the Bureau of Ento-
mology and Plant Quarantine. Benzol is used to kill
the screw worms. Pine-tar oil is used as a dressing for
wounds and for repelling flies.
Before these materials are applied, the portions of
the animal covered with discharges from the wounds
should be carefully cleaned. Wounds containing blood
and serum must be carefully swabbed with cotton,
because benzol does not readily kill screw worms pro-
tected by fluids in the wound. Immediately following
the swabbing, a light application of commercial benzol
is made to the wound with an oil can or syringe, which
retards the flow of blood. Three or four minutes
should be allowed for the benzol to reach the screw
worms. A second light application is then made, and
dry cotton is inserted in the opening of the wound.
This cotton plug should remain in the wound so that
the screw worms can have sufficient time to breathe
and be killed by the gas of the benzol. It is recom-
mended that stockmen leave the cotton plugs and screw
worms in the wounds.
Pine-tar oil (specific gravity 1.065, acid free,
dehydrated) is then applied over the cotton plug and
on the skin around the injured parts. It may be spread
with cotton wrapped around a clean stick. The pine-
tar oil repels flies and aids in healing. Following the
first treatment, the reappearance of a bloody discharge
from the wound indicates that living larvae are present.
In such cases treatment with benzol should be repeated.
If there is no further discharge, the condition suggests
that the screw worms were killed and that only pine-tar
oil should be applied. It is necessary to apply pine-tar
oil every day or two until the wound has healed.
HOW TO PREVENT SCREW
Screw worms must be prevented from breeding in
living animals. This is the only method known at pres-
ent for the control of the true screw worm fly. They
cannot be destroyed or prevented from infesting
animals by setting out flytraps or by burning dead
animals because they are rarely attracted to traps and
do not breed in carcasses.
If this fly can be kept from breeding in living
animals, it is believed that there will be little trouble
from screw worms.
EYE OF STEER
FlAi OF FW AHD CHUTE
FOR EOPE AILlIa R AE STOCK
Psts for dxute 9T 6
Pots forpm 7-" 57
Poles for p anl 16,5" 95
Ples for gate bm 1o5" 15
P&s for de dr1We uFr 5
R!es frp aW xbans 54V 9
Mls 40d Z5 Ibs
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UNIVERSITY OF FLORIDA
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