Insects in relation to national defense


Material Information

Insects in relation to national defense
Series Title:
Its Circular no. 1-23. Feb. 1941-Jan. 1944
Added title page title:
Insects in relation to national defense, circular
Physical Description:
24 nos. in 1 v. : ill., photos., map, plans, diagrs. ; 23 cm.
United States -- Bureau of Entomology and Plant Quarantine
U.S. Govt. Print. Off.
Place of Publication:
Publication Date:


Subjects / Keywords:
Beneficial insects   ( lcsh )
Insect pests   ( lcsh )
Insecticides   ( lcsh )
Fumigation   ( lcsh )
World War, 1939-1945 -- Health aspects   ( lcsh )
serial   ( sobekcm )
non-fiction   ( marcgt )


General Note:
Reproduced from type-written copy.
General Note:
Includes bibliographical references.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029081698
oclc - 09471812
lcc - SB931 .U44
System ID:

Full Text




TO 0


Circular 18


June 1941

I o p-Ro

Digitized by the Internet Archive
in 2013




Circular 18 Screwworms

Table of Contents

Introduction.............................. 1
Distribution............. .. .......... ... 2
How Man and Animals Are Attacked.......... 2
Life History andStages................... 3
Methods and Rapidity of Spread............ 5
Control................................... 6
Methods of Avoiding Attack on Man....... 6
Methods of Avoiding Attack on Horses
and Mules............................* 7
Prevention of wounds................. 7
Treatment of wounds.................. 7
Burning of carcasses.................* 7
Treatment of Human Infestations.......... 9
Treatment of Infestations in Animals...... 9
Source of the Materials................. 12
References...............................**o****** 13


The adult of the true screwworm (Cochlio-
myia americana C. & P.) is a bluish-green fly
that in its maggot stage lives as a true para-
site of man and other warm-blooded animals.
It is a native of the Americas and is largely
confined to the warmer climates, though during
summer it may extend its ravages to the cooler
regions. The extent of loss in countries other

Circular 18 Screwworms

than the United States has never been computed,
but in this country the annual loss has been
estimated at 5 to 10 million dollars.

This loss is caused mainly by the pene-
tration of the larvae into wounds of livestock
and infestations of the naso-phrangeal region
in man. No specific disease is known to be
carried by this insect, although it may intro-
duce into wounds various disease organisms.


The screwworm is present in the southern
portions of the United States, Central America,
Mexico, the West Indies, and throughout South
America, except the southern portion.

In this country it overwinters normally
only in southern Texas, along the Balcones Escarp-
ment from Del Rio to San Antonio, and southward;
in extreme southern Georgia and throughout Flor-
ida; in southern Arizona and extreme southern
California. As the season advances it moves north-
ward from the overwintering area in Texas, some-
times as far as Nebraska, Iowa, Illinois, Indi-
ana, and from the overwintering area in the
Southeast to Tennessee and to northern Alabama
and South Carolina. The screwworm infests large
areas in Arizona and New Mexico, and in Cali-
fornia it occasionally invades the Sacramento


The flies are attracted to wounds of var-
ious types upon which they feed and lay eggs.
Even slight bloody discharges are attractive,
as in the case of men with nasal catarrh. The
larvae, upon hatching, start feeding in the

Circular 18 Screwworms

wound, causing extensive destruction of tissue
and a bloody discharge of a peculiar, fetid
odor which is highly attractive to flies of
all kinds. These in turn infest the wound,
and if neglected it is enlarged rapidly. The
tissues around the infested wound become greatly
swollen and pockets are eaten out beneath the
skin. The infested man or animal may die due
to tissue destruction and the poisons absorbed
from the wound. Screwworms do not breed in
carcasses, but if the worms are 2 days old or
more when the animal dies they may complete
their growth in the carcass. Blowflies some-
times initiate infestations in wounds and often
occur in wounds after an initial attack by
screwworms. These blowflies breed in carcasses
(Circular 8).

Horses and mules are most frequently at-
tacked in scratches, wire cuts, saddle and har-
ness sores, and in the sheaths owing to local


The adult of the screwworm is a bluish-
green medium-sized fly with three dark stripes
on the thorax, Fig. 1. It deposits dense mas-
ses of whitish eggs. These are stuck firmly
together and to the tissue around the wound,
Fig. 2. The flies live from 2 to 10 weeks and
deposit from 2 to 12 masses of eggs. The eggs
hatch in 11 to 21 hours. The larvae feed close
together and are usually seen with the head
downward and the blunt tail end upward for
breathing. When full-grown, the larvae are
about 2/3 of an inch long and appear pinkish
in color and the rings of spines around the
body are rather prominent, Fig. 3. The larvae

Circular 18 Screwworms

Figure 1 Screwworm fly (note the three
dark stripes on thorax).

become full-grovn in 4 to 10 days and crawl
out of the wound, drop to the ground, and bur-
row into the soil 1/4 to 2 inches. The pupa,
or resting stage, Fig. 4, is passed in the
soil in about 7 or 8 days in warm weather and
it may last 2 months during the winter.

Soon after the flies emerge from the soil
they mate, feed, and are ready to lay eggs in
5 to 10 days.

The total cycle is completed in 18 to 30
days during the warmer months.

Circular 18 Screwworms

Figure 2 Fly depositing mass of eggs on a

Figure 3 Larva (note rings of spines).


The flight of the screw-
worm fly is strong and it has been
found that the pest migrates north-
ward with the advent of warm weath-
er at the rate of about 35 miles
a week. The pest is easily trans-
ported as worms in wounds, and often
infested horses, cattle, or sheep
are transported long distances and
the insect is thus introduced into

Circular 18 Screwworrms

uninfested territory many miles in advance of
natural spread. In such locations it may per-
sist until killed by frost and under favorable
conditions pass through several generations.

Figure 4 Pupa.

As screwworms breed in so many kinds of
animals and as the flies spread widely, control
in military bases and in the field must depend
largely on prevention of attack. The coopera-
tion of livestock owners in the vicinity of
camps may well be sought, looking toward the
avoidance of wounds during periods when screw-
worm flies are active, and the prompt treat-
ment of all cases to prevent the maturing of

Methods of Avoiding Attack on Man

Hospitals should be well screened.
Bloody bandages and clothing should be disposed
of promptly.
Men should avoid sleeping during the day
in screwworm territory without having the pro-


Circular 18 Screwworms

section of screens or bed nets. Those with
wounds or nasal catarrh should be especially
careful not to expose themselves.

Methods of Avoiding Attack on Horses and Mules

Prevention of wounds.--Injury of animals
should be avoided as much as possible. Prop-
erly fitted harnesses and good saddle blankets
prevent sores that may become infested. Brand-
ing and other operations that may lead to screw-
worm infestations should be performed, if pos-
sible, during periods when screwworm flies are
inactive or the animals should be confined and
the wounds watched until healed.

Treatment of wounds.--The recently devel-
oped ointment or smear referred to as Formula
No. 62 (see Circular E-540 in list of references)
is an excellent wound protector. Painting
wounds with pine tar oil (sp. gr. 1.065, acid
and water free) or pressing into them a small
quantity of finely ground diphenylamine crystals
prevents infestation for 1 to 3 days, but the
wounds should be watched until completely healed.
Severely wounded or infested animals are best
kept in screened stalls until the wound is par-
tially healed.

Burning of carcasses.--Carcasses of all
animals should be promptly burned. This pre-
vents the breeding of swarms of blowflies, and
if the animal was infested with screwworms when
it died, also prevents the maturing of these

The burning of a large carcass is most
easily accomplished by digging a trench in the
ground along the back of the animal. This
should be about the length of and slightly nar-

Circular 18 Screwworms

rower than the carcass and about 12 to 16 inches
deep. The trench is then filled with wood,
including some heavy sticks, and the carcass
is rolled over onto it. A fire is started at
the windward end, Fig. 5. In the course of a
few hours the carcass is completely consumed,
if the head and hoofs are pushed back on the
fire after the burning has progressed awhile.

Figure 5 Burning of carcasses prevents the
breeding of blowflies.

Circular 18 Screwworms


Early detection and treatment of human
infestations is important. Nasal infestations
are frequently not diagnosed for some time.
Pain, local swelling, the sensation of crawling,
and the presence of a bloody discharge are diag-
nostic features. The physician can often see
some of the larvae on careful examination.

Ether, chloroform, or benzol, introduced
into the nose with an atomizer or on a pledge
of cotton, followed by a blocking of the nostrils
with dry cotton, will usually anesthetize the
larvae and they can be removed with forceps or
by blowing the nose. In severe cases care should
be taken to avoid rupturing blood vessels that
may be expose by the larvae. Sometimes a sec-
ond or third application of the anesthetic is
necessary to dislodge all of the larvae, each
application for 2 or 3 minutes. After the lar-
vae are removed the care of the case is similar
to that of other wounds.


Commercial benzol (90%), applied to the
infested wounds with a rubber bulb syringe, is
excellent for killing the screwworms. If the
wound contains much pus or blood it should be
removed first with a cotton swab. The benzol
checks the bleeding. After a minute or two
more benzol is applied and a cotton plug lightly
inserted in the opening. In 3 to 5 minutes the
larvae should be dead and the cotton and larvae
should be picked out with a pair of sterile
blunt forceps, and the blood and pus cleaned
from around the wound. If blood is flowing,
apply more benzol and then paint the wound with
pine tar oil, or if the animal is not going to

Circular 18 Screwworms

be examined and painted with the fly repellent
daily, press into the wound a small amount of
finely ground diphenylamine crystals.

A combination screwworm killer and wound
protector has been developed recently by the
Bureau of Entomology and Plant Quarantine.
This ointment or smear, known as Formula No. 62,
is composed of the following:

(technical grade)...... 3g parts by weight
(commercial)........... 3g parts by weight
Turkey red oil
(pH-lO or neutral)..... 1 part by weight
Lamp black............... 2 parts by weight

The diphenylamine is dissolved in the
benzol, preferably by placing the two substances
together and allowing them to stand 12 or 24
hours. In no event should the dissolving of the
diphenylamine in benzol be attempted by heating
over an open flame. Benzol is highly inflammable
and should be kept away from flames and lighted
cigarettes or cigars. If heat is used to hasten
solution, the container holding the benzol and
diphenylamine may be placed in a vessel of hot
water, the container being left uncorked until
the diphenylamine is dissolved.

After the diphenylamine is dissolved the
turkey red oil is added and the mixture thor-
oughly shaken. The lamp black is then stirred
in gradually and the mixing continued until the
compound attains a smooth, even texture of about
the consistency of molasses. It is then ready
for use. The remedy is best applied with a
1-inch paint brush.

Circular 18 Screwworms

The following precautions should be
taken in preparing and using screwworm smear
No. 62.

1. Prepare the remedy well away from
open flames and do not have lighted cigarettes
or cigars around during the process.

2. Benzol, in the form in which it occurs
in the smear, is highly volatile and will evap-
orate quickly from the smear if left in an open
container. It is therefore advisable that the
smear be kept tightly covered in a cool place
when not in use. It is also recommended that
only an amount necessary for a few days? use
be removed at a time from the larger supply
container. Even when animals are actually being
treated the container should be kept covered
as much as possible. In case the smear, through
evaporation, becomes too thick for easy appli-
cation, an additional amount of benzol may be
stirred in to bring it back to its original con-

3. When infestations located near the eyes
are being treated, care should be taken not to
get an excessive amount of the smear into the
unaffected parts of the eye. If this is done
accidentally it is advisable to wash the eye
immediately with plain water, as the material
is irritating to the eyes.

4. Do not add oil, grease, or any other
substances to the formula, or its efficiency
will be greatly impaired, if not entirely de-

Circular 18 Screwworms

When using diphenylamine crystals or
Formula No. 62, the treatment need be applied
only every third or fourth day until the wound
is healed.

New treatments and control procedures
are being developed that are especially appli-
cable to ranch conditions where farmers and
stockmen may cooperate in suppressive opera-
tions on a large scale. If new problems arise,
additional information will be supplied by the
Bureau of Entomology and Plant Quarantine, upon

Source of the Materials

For the information of those who wish to
purchase the ingredients for the mixing of this
smear there is given below a list of companies
which manufacture t hem. No claim is made that
the list is complete, nor is any guarantee here
expressed or implied for the products of the
companies listed.

Diphenylamine should be obtainable from
the larger wholesale drug companies in screwworm-
infested territory. It is manufactured by the
following companies:

E. I. Du Pont de Nemours & Company, Inc.,
Wilmington, Delaware.
Lederle Laboratories, Inc., 30 Rockefeller
Plaza, New York, N. Y.
Eastman Kodak Company, Chemical Sales Division,
Rochester, N. Y.
The Dow Chemical Company, Midland, Michigan.

Circular 18 Screwworms

Turkey red oil is manufactured by the
following companies:

Apex Chemical Company, Inc., 200-214 So.
First Street, Elizabethport, N. J.
L. Sonneborn Sons, Inc., 88 Lexington
Avenue, New York, N. Y.

Lamp black is manufactured by the fol-
lowing companies:

General Carbon Company, Los Angeles, Calif.
The L. Martin Company (Germantown Eagle or
Velvet Brand), Tacony, Pa.
Whittaker, Clark & Daniels, Inc., 260 West
Broadway, New York, i. Y.


Bishopp, F. C. and others 1926 -- Screwwvorms
and Other
Bull. No.
857, U. S.
Dept. of
Bur. of
Bruce, W. G. and----------- 1936 -- Screwworms in
Sheely, W. J. Florida.
Bull. 86,

Circular 18 Screwworms

Dove, W. E. 1938 Screwwvorm Control.
Leaflet No. 162,
U. S. Dept. of
Bur. of Entomol-
ogy and Plant
Laake, E. W. and others 1936 Biology of the
Primary Screw
Wvorm Fly, Coch-
liomyia americana,
and a Comparison
of Its Stages
with Those of
Te chnical Bull.
No. 500, U. S.
Dept. of Agricul-
ture, Bur. of
Entomology and
Plant Quarantine.
Melvin, Roy and others 1939 Results of Studies
on Diphenylamine
as a 1.ound Pro-
tector Against
the Screwwvorm,
Cochliomyia amer-
icana C. and P.
Circular E-480,
U. S. Dept. of
Agriculture, Bur.
of Entomology and
Plant Quarantine.
Melvin, Roy and others- 1939 Diphenylamine as a
VIound Protector
Against the Screw-
worm, Cochliom ia
americana C. and P.
Circular E-481, U.
S. Dept. of Agricul-
ture, Bur. of Ento-
mology and Plant

Circular 18 Screwworms

Melvin, Roy and others 1941 -- A New Remedy for
the Prevention
and Treatment of
Screwworm Infes-
tations of Live-
stock. Circular
E-540, U. S.
Dept. of Agricul-
ture, Bur. of
Entomology and
Plant Quarantine.
Parman, Daniel C. and 1941 Ranch Management
Barrett, William L., Jr. for Screwworm
Prevention and
Eradication in
Texas and Adjoin-
ing States. Cir-
cular E-520, U.
S. Dept. of Agri-
culture, Bur. of
Entomology and
Plant Quarantine.


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