The wax moth and its control

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

Circular No. 386

Issued April 1936
Revised January 1942 @ Washington, D.C.

UNITED STATES DEPARTMENT OF AGRICULTURE

The Wax Moth and Its Control

By WARREN WHItTcoMB, Jr., apiculturist, Division of Bee Culture,
Bureau of Entomology and Plant Quarantine

CONTENTS

Page Page
Economicnmportances=22-—--- 2 eee eee 1A COntTO Sin ss aera ey aan eas eS Te 6
Wife bistonyes =e See eas Seo ese 2 Control measures in the apiary_____________ 6

TIM CXOG Cte See ee ens See Se Ros ee 2 Control measures for stored combs__________

EB YY EEN YD a a a 2 Fumigating and storing comb-section honey

AW AVS) j OS} O LOU Of = See es See Se gee eS ee ae 3 and honey in extracting frames___________

Ten UD as ses eee cies oe ee Ce ee eee 4 General directions for fumigation with para-

DY YS) GXOUD NS Soe Gree ee eee eee ae 4 dichlorobenzene, carbon disulfide, and
INumMbeROmbroodGe= seen = nee eee eee 5 Calciumicy anid eben eee 9

Other moths causing damage to stored combs... _ 5

ECONOMIC IMPORTANCE

The wax moth (Galleria mellonella (.))* is responsible for large
losses to beekeepers in the United States. It is found almost every-
where that bees are raised, but it does the greatest damage in the
Southern States because of the long season of activity.

Probably the most noticeable injury due to the wax moth is to
combs in storage, especially if they are in a warm, protected place.
Such injury consists in destruction of the combs by the larvae, which
leave them a mass of webs and debris (fig. 1). This type of damage
1s more common than the destruction of entire colonies. Weak,
diseased, starved, or otherwise abnormal colonies are a prey of the
wax moth, and in these colonies the combs are often entirely de-
stroyed. In such cases, however, wax moth injury is secondary;
strong colonies will defend themselves well against attack.

The larvae of the wax moth also do considerable damage to comb
honey. The eggs are probably laid on the comb or section boxes
before the comb-honey supers are removed from the hives, but the
damage does not become evident until some time after the honey has
been placed in storage. The damage consists of small, rather incon-
spicuous tunnels and borings through the thin wax caps of the honey
cells. The honey leaks out through these holes, making the affected
section unmarketable.

1This insect is also known variously as the bee moth, the bee miller, the wax miller,
the wax worm, and the webworm.

416141°—41

2, CIRCULAR 386, U. S. DEPARTMENT OF AGRICULTURE .

LIFE HISTORY
THe Eee

The egg of the wax moth is small, white, and rather incon-
spicuous (fig. 2). It measures about one fifty-fourth of an inch in
length and one-sixtieth of an inch in greatest width.

The eggs are probably laid most frequently in the cracks between
hive parts—that is, between supers, between hive body and bottom
board, or between super and cover. Egg masses have been found in

FIGURE 1.—Webs and tunnels made by larvae of the wax moth in a comb.

cracks between the inner cover and the top super of the hive, where
they had apparently been deposited by females from outside the
hive. Eggs are also laid inside the hive, almost always in places
farthest from the light. They are difficult to see and may often be
overlooked.

At 75° to 80° F. the eggs hatch in from 5 to 8 days, but at lower
pep ua (50° to 60°) the incubation period may extend to
35 days.

THE LarvA

_ The young larvae are often seen on the inner covers of hives and
in the cracks between supers and hive parts. They attempt to

THE WAX MOTH AND ITS CONTROL 3

burrow into the wax almost immediately after hatching. The first
burrows are often incomplete and may be mere roughenings of the
surface of the wax. After the first day, however, they make small
tunnels between the cells and toward the midrib of the comb.

The growth of the larvae depends chiefly on the quantity and
quality of their food and on the temperature. The length of the
larval period ranges from 28 days to 4 months and sometimes to
nearly 5 months. During this period the larvae grow from about
one twenty-fifth of an inch to seven-eighths of an inch in length.

The food of the larvae consists in part of impurities in the wax,
and in obtaining this food the larvae ingest the wax itself. Founda-
tion, especially in frames, is seldom attacked, and then usually only
by the small larvae. Although larvae can develop on foundation,

Figure 2.—Eggs of the wax moth laid on a comb. Greatly enlarged.

the mortality of such larvae is high, and the developmental period
of those that survive is relatively long. It is almost certain that
some of the damage reported by beekeepers as caused by the lesser
wax moth (Achrova grisella (¥.)) is the work of such poorly fed
larvae of Galleria mellonella.

The optimum temperature for the development of the larvae is
between 85° and 95° F., about that normally found in a beehive
during the active season. At 40° to 45° the larvae seem to become
dormant, and no feeding or growth takes place.

THE PREPUPA

When full-grown the larva spins a dense, tough, silken cocoon
Usually this cocoon is firmly attached to the side of the hive, the
frame, or other solid support, but some cocoons are found in the mass

4 GIRCULAR 386, U. S. DEPARTMENT OF AGRICULTURE

of tunnels and refuse of the wax on the frames or on the bottom of
the hive (fig. 3). Frequently the cocoon is placed in a hollow
chewed out of the wood of the hive or frame. Frames may be found
in which holes have been chewed completely through the end or top
bars, with the cocoon and pupal case inside these holes.

Tue Pupa

Within the cocoon the larva changes to the pupa. The duration
of the pupal stage within the cocoon ranges from 8 to 62 days,
depending on the temperature. As with many other insects, the
pupal period allows the wax worm to pass through the fall and
winter protected against climatic influence. In the South, especially
in warm winters, the adults may emerge at any time.

FIGURE 3.—Pupal cases, or cocoons, of the wax moth.

THE ADULT

The normal adult wax moth is about 84 inch in length and has a
wing spread of about 1 to 114 inches (fig. 4.) Adults are commonly
seen in the resting position a their grayish-brown wings folded in
rooflike fashion (A and B). The moths are not easily disturbed, but
when molested they run rapidly before they take wing. The males are
shghtly smaller than the females and may be distinguished from them
by the shape of the outer margin of the fore wing, which is notched in
the male but smooth in the female, and by the absence of palpi, which
are prominent in the female.

The moths vary widely in size and color, according to the type
of food consumed by the larvae and to the length of the developmental

THE WAX MOTH AND ITS CONTROL 5

period. Small, poorly nourished larvae, or those which, because of
low temperatures or other factors, develop slowly, transform into
smal] adults, sometimes less than half the normal size. Larvae fed
on dark brood combs transform into adults which may be dark gray
to almost black, while larvae reared on foundation become silvery-
white moths, which are smaller than those reared on brood comb.

The female starts depositing eggs from 4 to 10 days after emer-
gence and continues depositing them as long as her vitality lasts.
Egg laying may be rapid at times, and as many as 102 eggs have
_ been deposited by a female in 1 minute. The total number of eggs
laid by a female varies considerably, but it is usually less than 300.
The adults may live as long as 3 weeks.

Ee oa

Beans Deane zs Seen es aon oe Beane ca ss ie

Figure 4.—Adults of the wax moth: A and B, With. wings folded; C and D, with
wings spread; A and C, females; B and D, males. Note the deep clefts in the
tips of the fore wings of the male.

NUMBER OF BROODS

It seems doubtful that there are definite generations of the wax
moth during different periods of the year in the Southern States.
Rather it is probable that the moth is always present, that larvae
in all stages, pupae, and adults may be found at any time, and that
development is continuous except during periods of low temperature.

OTHER MOTHS CAUSING DAMAGE TO STORED COMBS

The lesser wax moth (Achroia grisella) also does some damage to
stored combs. Its work is similar to that of the wax moth, but the
tunnels are smaller, the webs finer, and feeding and webbing are more
confined to the outer surface of the combs. The Mediterranean
flour moth (E£phestia kuehniella Zell.) is a pollen feeder but does
some damage to combs by boring tunnels through the midrib. This
moth also tunnels into brood cells and consumes the food intended
for the developing bee larvae. These two moths may be controlled
by the methods given for the wax moth.

6 CIRCULAR 386, U. S. DEPARTMENT OF AGRICULTURE

CONTROL

ConTROL MEASURES IN THE APIARY

Beekeeping practices and manipulations should be based on the
assumption that the wax moth in some stage may be present in the
hives at all times. The bees are the most effective natural enemies
of wax moths. The bees will, when the colony is strong, carry
the moths out of the hive, and there is no better insurance against
the ravages of the pest than to have strong queenright colonies. Ac-
cidental loss of queens in colonies late in the fall may mean the loss of
colonies from wax moth damage before the first spring examination.

In addition to strong colonies the best control measure is cleanli-
ness of hives—removal of propolis, bur combs, and refuse on the
bottom board, which provide protection for larvae of the wax moth,
even in strong colonies.

From the standpoint of both productive beekeeping and wax
moth control, box hives or hives in which the frames are not easily
movable should be replaced by modern equipment. Such hives give
the wax moth an opportunity to reproduce, and they provide breed- —
ing places from which other colonies may be attacked.

Control of the wax moth by trapping the adults at lights or by
means of trap combs has not been successful.

CoNnTROL MEASURES FOR STORED Comps

Since light and air repel both the adult moths and the larvae,
stored combs will be less subject to destruction if they are exposed
to the light by setting the supers on end and spaced to allow ven-
tilation. The common method of storing combs in tightly closed,
crowded hive bodies is highly favorable to wax moth infestation
and development.

The use of chemicals to kill the wax moth has proved the most
satisfactory measure thus far for controlling this insect in stored
combs. Several fumigants have found favor for this purpose, par-
ticularly paradichlorobenzene, carbon disulfide, and calcium cyanide.
Other fumigants that have been used include fumes from burning
sulfur, carbon tetrachloride, and methyl bromide. These materials
have been found to kill all stages but the egg, and methyl bromide is
even effective against the eggs of the wax moth. Some of these fumi-
gants, however, have definite limitations; on others not enough research
work has been done with the wax moth to justify recommendation of
their use to beekeepers.

PARADICHLOROBENZENE

Paradichlorobenezene (“PDB”) is a white crystalline substance
which evaporates slowly in air. The gas is not unpleasant to smell
and when used as directed will not be found injurious to people. Higher
concentrations, however, are irritating, and the crystals must be
handled in such a manner as to prevent their being taken internally
by accident. It is heavier than air, noninflammable, and nonex-
plosive.

In paradichlorobenezene fumigation the supers should be stacked
as tightly as possible and the cracks between them covered with

THE WAX MOTH AND ITS CONTROL Z

strips of gummed paper (fig. 5). Three ounces of the crystals to a
stack of five 10-frame hive bodies may be sprinkled directly on the
top bars of the frames, as in figure 5, or preferably put on a piece
of paper or cardboard laid on the top bars. The cover should then
be put tightly in place. Since the gas is nonpoisonous and not dis-
agreeable, treatment may be made in ordinary storage, it being un-
necessary to take the infected material out of doors. At intervals
during the storage season the covers of the stacks should be raised,
and if no crystals are still present more should be added.

FieureE 5.—Supers loaded with comb ready for fumigation. The joints are
sealed with gummed paper tape, and the crystals of paradichlorobenzene have
been sprinkled heavily over the top bars.

Paradichlorobenzene is most effective at temperatures above 70° F.
and volatilizes more rapidly as the temperature rises. Stored materials
should be inspected at intervals of 2 or 3 weeks, depending on the
temperature of the storehouse and the prevalence of moths.

CARBON DISULFIDE

Carbon disulfide has been a standard fumigant for wax moths and
similar insects until recently, and with proper precautions it is still
considered satisfactory. The commercal product is a yellowish,
somewhat oily liquid, which changes readily at ordinary temperatures
into an ill-smelling gas. The liquid i is about one-fourth heavier than
water, and the gas is heavier than air. It is highly inflammable,
and the vapor is explosive when mixed with air in certain pro-
portions; therefore, this chemical must not be handled around
fire of any kind. At certain concentrations it can be ignited by

8 CIRCULAR 386, U. S. DEPARTMENT OF AGRICULTURE

hot steam pipes. Preferably it should be used out of doors or in
a well-ventilated or open shed.

For carbon disulfide fumigation the supers should be sealed in the
same manner as for paradichlorobenzene. One ounce of liquid is
sufficient for five supers, and more than this number of supers should
not be placed in a single stack, because the gas, being heavy, quickly
sinks to the bottom of the stack and may not adequately fumigate
the top super. The stack should remain sealed for not less than 12
hours. Since carbon disulfide is not effective against the eggs of the
wax moth, it may be necessary to repeat the treatment after any eggs
have had time to hatch.

CALCIUM CYANIDE

Calcium cyanide is obtainable either as a dust or as fine or coarse
crystals. For use in fumigating bee equipment the crystals, contain-
ing not less than 40 percent of calcium cyanide, are preferable to the
dust. In the presence of moisture, such as that in the air, the crystals
release a deadly gas, which is noninflammable and nonexplosive as
ordinarily used in fumigation. It is, however, extremely poisonous |
to people and animals, and care must be taken not to breathe the
gas, the pronounced odor of which is discernible when the con-
tainer is opened. The fumigation should be conducted out of
doors, and it is safer to wear a suitable gas mask when handling
calcium cyanide in any form. For use, put 1 tablespoonful of
crystals on a sheet of paper and place the paper on top of the frames
inasuper. Quickly place the other supers on top, using not more than
five supers per stack, and tape the joimts between supers with
gummed paper tape. The stacks of supers should not be disturbed
for 24 hours after fumigation, and the combs should be well aired
before they are used.

FUMIGATING AND STORING CompB-SECTION HoNEY AND HONEY IN
EXTRACTING FRAMES

The control of wax moth damage in honey stored in comb sections
or in frames is the same as for other stored combs. Honey, however,
absorbs odors readily, and the odor of paradichlorobenzene is
absorbed and held easily, being especially objectionable in mild-
flavored honeys. The gas given off when calcium cyanide comes in
contact with the moisture in the air is not absorbed by honey.
Calcium cyanide dust should not, of course, be applied directly to
honey in the comb, but should be placed on a cardboard or in a con-
tainer of some sort. Stored honey should not be exposed to any
fumigant for long periods.

Much of the honey produced for market in comb sections is mild
in flavor, and the absorption of even slight amounts of a foreign
odor is objectionable. Carbon disulfide is the most satisfactory:
fumigant for comb honey. As soon as sections are well sealed, they
should be removed from the hives, placed,in supers, and stacked
not more than 8 to 10 high. The directions given previously for
fumigating combs can be followed, with due care for the inflammable
and explosive nature of this fumigant.

THE WAX MOTH AND ITS CONTROL Q

After fumigation the comb-honey sections should be stored in a
moth-free room that is clean, well lighted, and ventilated to dis-
courage the wax moths, which prefer to lay their eggs on beekeeping
equipment in dark, poorly ventilated places.

Honey is best protected by extracting it as soon as possible after
removing it from the hives, since in tin or glass containers it is safe
from attack by wax moths, mice, ants, or other pests, as well as from
contamination by fumigants or other odors. Beekeepers sometimes
wish to store full frames of honey, or extracting may have to be
delayed. In either event if there is danger of infestation by wax
moths, the honey should be fumigated as indicated for comb-section
honey.

Paradichlorobenzene may be used for fumigating frames of honey
that are to be fed back to the bees, for bees do not object to a slight
odor of this chemical, but this fumigant should not be used to protect
frames of honey that are to be stored for long periods and then
extracted with the intention of marketing the honey, as the odor
is definitely objectionable to consumers.

GENERAL DIRECTIONS FOR FUMIGATION WITH PARADICHLOROBENZENE,
CarBon DISULFIDE, AND CALCIUM CYANIDE

(1) Use not more than five supers in a stack and seal the joints
with gummed paper tape to make the stack as nearly gastight as
possible. With gases heavier than air, make sure that the base of
the stack is tightly closed, since the gases sink to the bottom of the
stack and may escape. A pad of newspapers placed beneath the
stack will help to confine the gas.

(2) If calcium cyanide is used, fumigate out of doors. The same
applies to carbon disulfide if there is the least danger of fire; at all
events apply the latter in a well-ventilated room. Read carefully
the directions for using the selected fumigant and have everything
ready before beginning the fumigation.

CAUTION.—Carbon disulfide gas is highly explosive, and any
chance of ignition must be carefully guarded against. Carbon
disulfide and calcium cyanide and their gases are poisonous to
people and to animals, and must therefore be stored and handled
with extreme care.

(3) To fumigate with paradichlorobenzene, put the crystals on
a piece of paper and lay it on the top bars of the top super; renew
them as needed.

(4) Since paradichlorobenzene, carbon disulfide, and calcium
cyanide are not effective against eggs of the wax moth, subsequent
fumigations may be needed. If the temperature following the first
fumigation is about 70° F., it is well to repeat the treatment after
about 2 weeks. The fumigated stacks should be left sealed for
about 24 hours.

(5) Following fumigation, air the combs thoroughly before using
them in the apiary.

Table 1 gives an outline for reference in fumigating stored combs
and honey against the wax moth.

CIRCULAR 386, U. S. DEPARTMENT OF AGRICULTURE

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ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE
WHEN THIS PUBLICATION WAS EITHER FIRST PRINTED OR LAST REVISED

NSECTELOrYy OF Agriculture.) see CLAUDE R. WICKARD.

Cher CCl Clary as an ee Se ee a PAUL H. APPLEBY.

AISStSLONT: SCOT CLIN Y ae ee oy eee GROVER B. HI.

Darectorop Un pormaiones 222 a eee Morsp SALISBURY.

Durector of Extension Work. = =~ = = M. L. WILSon.

DU CCCOE Ole HiNQnee == so een ees ee W. A. JUMP.

Di CClOr Of ve ChSONNCL = Se ele ye Soke ee T. Roy REI.

DAF CCLOR Of VCSCOT Chit saat es JAMES T. JARDINE.

PG CCLOT Of MO Ket TGs sae Roy F. HENDRICKSON.

IS U4 CUE OR ceria ee Se I | 2 MASTIN G. WHITE.

PNG USC{C OOTOINOLOT =< 2s ee ee M. S. EISENHOWER.

Office of Piant_ and Operations_________-_____ ARTHUR B. THATCHER, Chief.

Ojice a, C: & CleAChviticse 22a ee FRED W. MorreE.L1, Chief.

Office of Hxperiment Stations____-—_-__--~_=— JAMES T. JARDINE, Chief.

Office of Foreign Agricultural Relations_____- LESLIE A. WHEELER, Director.

Agricultural Adjustment Administration_____ R. M. Evans, Administrator.

Bureau of Agricultural Chemistry and Engi- HENRY G. KNicHT, Chief.
neering.

Bureau of Agricultural Economics_________-- H. R. Tottey. Chief.

Agricultural Marketing Service___--__-+---~~ C. W. KITCHEN, Chief.

Bureau of Animat Indusiry——__ 2 =~ JOHN R. MOHLER, Chief.

Commodity Credit Corporation________---___ J. B. Hurson, President.

Commodity Exchange Administration___----~ JosEPH M. MEHL, Chief.

Bureau of Dairy Industry_—-__—-2--___=———~- O. E. Reep, Chief.

Bureau of Entomology and Plant Quaran- P. N. ANNAND, Chief.
tine.

Farm Credit Administration______._-__._--+--- A. G. Buack, Governor.

Farm Security Administration______-~___---- C. B. BALpwIn, Administrator.

Federal Crop Insurance Corporation_—-_~~-~_-_. Leroy K. SmMiTH, Manager.

TE OGE Sta NCU AG Ces tee ae ee ee EARLE H. Cuapp, Acting Chief.

Bureau of Home Heonomics._————-~2=— = = LOUISE STANLEY, Chief.

RUA a ferns Werner ties ee oe DS eS RALPH R. SHAW, Librarian.

Bareat-of Plantundustry—_.— = -- 3 BE. C. AUCHTER, Chief.

Rural Electrification Administration_____---- Harry SLATTery, Administrator.

Sot Conservation Service____-----_---_----- H. H. BENNETT, Chief.

Surplus Marketing Administration___-__----- Roy F. HENDRICKSON, Adminis-
trator.

This circular is a contribution from

Bureau of Entomology and Plant Quarantine P. N. ANNAND, Chief.
Division. of Bee Culture_________~----~- Jas. I. HAMBLETON, Principal Apt-
culturist, in Charge.

11

U.S. GOVERNMENT PRINTING OFFICE: 1941

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