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




T 0


Circular 14


June 191+1




Circular 14 Chiggers

Table of Contents
Introduction............................. 2
Distribution................. .... ........ 2
Seasonal Occurrence...................... 3
Hosts....... ..... ... .. ..... ... ........ 3
Life History and Methods of Attack....... 4
Appearance and Stages.................. 4
Chiggers Do Not Burrow Into the Skin... 5
Place of Attack........................ 5
Diagnosis and Lesions........***........... 6
Control... .. .. ... .. .. .. ... .. .... .. ... 7
Prevention of Attack on Man........... 7
Clothing................. ............ 7
Sulfur dust as a protector........... 7
Removal of Chiggers and Treatment
of Bites............................. 8
Elimination of Chiggers from Grounds... 8
Removal of underbrush and cutting of
weeds and grass................... 8
Sulfur dusting of infested areas..... 9
References. .. .. . ..... .. .. . . .. ........ 9

Circular 1 Chiggers


Chiggers, red bugs, jiggers, or harvest
mites, Eutrombicula alfreddugesi (Oudemans),
as they are variously called, are the larvae,
or first active stage of a large scarlet soil-
inhabiting mite. Although the chiggers found
in the United States are not known to carry
any disease, they produce extreme annoyance to
man by their bites. The intense itching caused
by these pests often interferes with sleep and
the poison injected may cause fever and loss of
appetite. Infection is often introduced as a
result of scratching. This may produce trouble-
some local sores, and boils sometimes result.
The annoyance caused by chiggers often has marked
effect on the activities of individuals, and the
efficiency of military units operating in heav-
ily infested areas may be materially reduced.
M.en not accustomed to chigger attack usually
suffer most, though some never seem to acquire
any degree of tolerance. Chigger establishment
and the effect of their presence vary greatly
with individuals, some of whom are entirely
immune to chigger attack.


In general chiggers are more troublesome
throughout the Southern States. They are, how-
ever, rather abundant in eastern Kansas, in Mis-
souri, the southern portions of Illinois, Indi-
ana, Ohio, Virginia, and southern Maryland. They
are present locally in some more northern.States,
such as Iowa, southern Minnesota, and Wisconsin,
and also in Pennsylvania. Scattered occurrences
are reported northward along the east coast to
Cape Cod, Massachusetts. They are not found in
the western part of the United States, although
some are present along streams in central western

Circular 14 Chiggers

There is considerable local variation in
chigger abundance. They prefer bottom lands
and areas overgrown with weeds and brush, although
they may be abundant on moist areas where weeds
and brush are practically absent. They are
notoriously bad in most areas overgrown with
briars or blackberry bushes. They may occur,
however, on well-kept lawns, especially the first
year or two after an area has been cleared and
developed. They are usually more abundant on
heavy soils than on light sandy ones.


The seasonal activity and abundance of
chiggers vary with the latitude and also with
the weather conditions.

In portions of the country where hard
freezes do not occur they may be present, though
less abundant, throughout the winter. Somewhat
farther north they become active about April 1,
and toward the northern limits of their range,
Mlay 1 or later. Their first appearance in spring
is usually at the time blackberries begin to
bloom. At the latitude of Dallas, Texas they
reach a peak of abundance about June 1, and their
activity continues until heavy frosts occur (usu-
ally about November 15). Hot, dry weather in
midsummer reduces their numbers, especially in
exposed places.


Chiggers are of most importance as pests
of man; but horses, mules, dogs, and cats are
sometimes annoyed if heavily infested. They
attack and seriously injure or kill young chickens,
turkeys, and wild birds. They also attack rab-

Circular 14 Chiggers

bits and other wild animals and snakes, lizards,
and toads.


Appearance and Stages

Chiggers are the first, or six-legged,
stage of a large scarlet-colored velvet mite.
They are just large enough to be readily seen
with the naked eye, Fig. 1. They crawl about
rapidly. When
engorged the body
becomes distended
and about 1/32 of
S\an inch in length.
/ The red color is
v usually less intense
after engorgement
/ than before.

Figure 1 A chigger, or red

When engorged
with the blood of
man or some animal
the chiggers drop
off and later, on
the ground, molt
their skins. The
subsequent stages
of the mites are
not injurious in
any way. They live
as scavengers on
decaying vegetation.

The mites become full-gromwn in the fall
and burrow in the soil from 1/4 to 1 inch and
remain there during the winter. In the spring

Circular 14 Chiggers

they deposit a mass of eggs. These hatch sev-
eral weeks later and the young apparently live
several months if they do not find a host.

Chiggers Do Not Burrow Into the Skin

It is a common belief that chiggers bur-
row into the skin. This is not the case. They
attach to the skin, usually close to a hair,
Fig. 2, and inject an irritating secretion which
continues to cause severe
|itching for several days
after they have dropped
|off or have been removed.
Normally the chiggers
become engorged in 4 to
wll\ 6 days and drop off,
but in the case of man
they are usually scratched
off within a day or two
l after the itching begins.

L |Place of Attack

-- -. A

Chiggers may at-
tack any part of the
body. As they usually
crawl up from the soil
and vegetation, however,
they are likely to infest
the lower extremities
most heavily. They are
inclined to stop crawling
up and attack where there
is some obstruction, as
under hose supporters or
belts. They may become

Figure 2 Cross section of
skin showing a chigger attached
at base of hair.


Circular 14 Chiggers

well distributed over the entire body in cases
where men find it necessary to lie or crawl on
the ground. They may occur in the hair of the
head, but as a rule are not troublesome there.


Few people detect the presence of chiggers
until they have been attacked for 2 to 12 hours.
Itching usually starts in about that length of
time and becomes more intense for the next day
or two.

Accompanying the itching there usually
develop raised whitish wheals from 1/4 to 1/2
inch in diameter, with a s1uall reddish area
around the chigger, which can be seen as a min-
ute red point at the center. Later a small
blister develops at the center. These blisters
are usually broken and the chi,-er destroyed by
scratching. Then a bright rec area remains,
and the itching may persist for a period of 4
to 10 days after the infestation occurred. If
secondary infection is introduced the lesions
may persist for weeks.

Those not familiar with chiggers often
mistake an infestation for sormie disease. The
distribution of the spots, the intense itching,
and the small blister-like center of the lesion
readily distinguish chigger infestations frou
other skin irritations. This is particularly
true if an examination is :.ade early '.,-hile the
chiggers are present.

Circular 14 Chiggers


Chiggers are so widespread and develop
on so many forms of animal life that it is
almost impossible to control them over large

Prevention of Attack on :Man

Clothing.--Closely woven garments with
boots worn over the trousers will exclude many
of the chiggers. Leggings if closely fitted
over the shoes offer much protection, but some
find their way under the leggings. Chiggers
are able to pass through light clothing of open

Sulfur dust as a protector.--Dusting the
clothing and body, especially from the waist
down, with sulfur gives almost complete protec-
tion against these pests, ordinary flowers of
sulfur will suffice, but the finer sulfurs (325
mesh) are better.

One should lightly dust sulfur on the skin,
underclothes, and socks before going into chigger-
infested areas. The effectiveness of the sulfur
increases after it has been applied 2 or 3 days
in succession, at which time it can be relied
upon to give reasonably complete protection.

There are some who are sensitive to the
repeated application of sulfur. If skin eruption
results from sulfur, its use should be discontin-
ued. Sulfur is somewhat objectionable because
of the odor produced, especially when it is hot
and the treated individuals are perspiring. It
also discolors gold and other metal articles.
Those who are susceptible to chiggers readily over-
look these objections, however, because of the
relief obtained.

Circular 14 Chiggers

Repellents other than sulfur have been
suggested, such as kerosene applied to the shoes
and outer clothing, but none of these is as sat-
isfactory on the whole as sulfur.

Removal of Chiggers and Treatment of Bites
'.Then a person is exposed to chiggers without
having previously applied sulfur, a warm bath
should be taken at once and all clothing changed.
It is well to lather the body thoroughly with a
soap containing sulfur or cresol and let the
lather remain on 5 or 10 minutes before washing
it off. Other soaps are reasonably effective if
medicated soaps are not at hand. If there is
certainty that chiggers have attached to the
skin, a light application of kerosene or pyre-
thrum-oil fly spray to the body 2 or 3 minutes
before bathing is advised. Caution. These
materials may irritate the skin if left on too

There is little that can be done to allay
the itching, other than to kill the chiggers as
soon as possible and apply cooling lotions such
as mentholated ointments or carbolated petrolatum.
The application of collodion ("new skin") to each
chigger bite is soothing.

Scratching should be avoided as far as
possible. After the chiggers have been destroyed
by the above methods a cold shower bath continued
for some time may be employed. This tends to
reduce the fever and local burning. Bathing in
salt water, especially sea water, is also helpful.

Elimination of Chiggers from Grounds

Removal of underbrush and cutting of weeds
and grass.--Chigger abundance can be reduced by

Circular 14 Chiggers

clearing out underbrush and keeping grass and
weeds closely cut. The clearing operation
should extend back some distance (50 to 100
feet) from the camp grounds.

Sulfur dusting of infested areas.--Some
degree of control of chiggers can be secured
by dusting the vegetation and ground thoroughly
with 325-mesh sulfur. This treatment is most
effective if supplemented with the clearing and
grass cutting mentioned above. The sulfur
should be applied at the rate of 50 pounds per
acre with a dust gun (see Circular 20). The
frequency of such applications to accomplish the
greatest good has not been determined, but it is
suggested that three or four applications be
made at intervals of 2 weeks, beginning at the
early part of the chigger season.


Bishopp, F. C. 1930. Red bugs, or chiggers,
and their control. U. S. Dept.Agr.,
Bur. of Entomology. E-281.

Ewing, H. E. 1921. Studies on the biology and
control of chiggers. U. S. Dept. Agr.
Bulletin No. 986.

Miller, A. E. 1925. Clover mites and chiggers.
Ohio Agricultural Experiment Station,
Wooster, Ohio, Bimonthly Bulletin,
vol. X, no. 7.

Riley, William A. and Johannsen, Oskar A. 1938.
Medical Entomology. Second Edition.
McGraw-Hill Book Company, Inc.


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