UNIVERSITY OF CALIFORNIA

COLLEGE OF AGRICULTURE

AGRICULTURAL EXPERIMENT STATION

BERKELEY, CALIFORNIA

CIRCULAR 342
July, 1937

ANTS AND THEIR CONTROL
IN CALIFORNIA^

J. E. ECKERT^ AND ARNOLD MALLIS^

1. — The Argentine ant, greatly enlarged. This is the most
important ant pest in California. (From Cir. 38.)

LIFE HISTORY AND HABITS
Ants have occupied the attention of man from early times because of
their almost universal distribution, their peculiar habits of life, and
their general economic importance in the field and home. They are found
everjrwhere on land, from the highest mountains to areas below sea level,
from deserts to dense forests. In total numbers they far exceed any other
group of terrestrial animals. Like the social bees, termites, and wasps, in-

^ This publication supersedes Circular 38, The Argentine Ant in California, and
Bulletin 207, The Control of the Argentine Ant, both by C. W. Woodworth.

* Assistant Professor of Entomology and Assistant Apiculturist in the Experiment
Station.

^ Graduate Student in Entomology.

University of California — Experiment Station

Fig. 2.— The egg of the
Argentine ant, greatly en-
larged. (From Bui. 207.)

Fig. 3. — A very young
larva of the Argentine ant,
greatly enlarged. (From
Bui. 207.)

Fig. 4. — A full-grown
larva of the Argentine ant,
greatly enlarged. (From
Bui. 207.)

Fig. 5. — The pupa of a
queen of the odorous house
ant (Tapinoma sessile),
greatly enlarged. (Fl-om
Bui. 207.)

dividual ants cannot survive alone but must live in communities where
they can profit by the extraordinary adaptability of the entire popula-
tion to changes in the external environment. Unlike the other social in-
sects, however, the ants have so specialized their mode of living as to
become responsive to changing conditions and less dependent upon a
definite habitation. They do not require complex materials with which to

CiR- 342] Ants and Their Control 3

build their nests nor specially fabricated compartments in which to rear
their young. Their nests may be found in the open ground, under stones
or wood, in decaying trees, or in any structure that affords the desired
protection. They can transport their eggs, larvae, or pupae (figs. 2, 3, 4,
and 5 ) from one place to a more favorable location at a moment's notice
and thus are not bound to any particular situation.

Ants have another distinct advantage in that the span of life of the
individual is much greater than for most social insects, extending over
years instead of only a few weeks or months. They are also comparatively
free of enemies, their greatest menace being other species of their own
family.

All ants belong to a single large superfamily — the Formicoidea —
composed of some 8,000 or more described species, subspecies, and varie-
ties. In California approximately 175 different species have been identi-
fied, and many others are undoubtedly present. Fortunately, however,
only a very small percentage of this number have noxious habits of any
great economic importance. On the other hand, many species are bene-
ficial primarily through aiding in the destruction of organic substances
and of living insects. Most of the smaller forms of animal life and par-
ticularly insect life that die are soon cut up and devoured by ants. The
extent of this one service alone to mankind is often overlooked or under-
estimated.

The noxious ants cause injury in many ways. Some invade dwellings
and make forays on sweet or fatty substances. The mere presence of ants
searching for food in the kitchen, pantry, storeroom, or warehouse
causes most persons to attempt drastic means of exterminating them.
The Argentine ant is, without doubt, the most important household pest
in California (fig. 1). Also important in this regard are the odorous
house ant, the California velvety tree-ant, the pyramid ant, the Cali-
fornia fire ant, the western thief ant, Pharaoh's ant, the tiny black ant,
the pavement ant, and the carpenter ants of the genus Campanotus. At
times certain species of the field ants, of the genus Formica, as well as
other forms, may be temporary invaders of the home.

Besides being household pests, ants may damage lawns, gardens, seed-
beds, fields, or orchards by their nesting habits and by destroying plants,
fruits, seeds, and nuts. Certain field ants feed on the saccharine excre-
tions of plant-sucking insects such as mealybugs (Coccidae), tree hop-
pers (Membracidae), and plant lice (Aphididae), which they have
formed the habit of pasturing and guarding. Sometimes such ants must
be destroyed in order to control other destructive insect forms. In Cali-
fornia, the Argentine ant is the most important offender in the field and

4

University of California — Experiment Station

orchard in caring for honeydew-excreting insects. The agricultural or
harvester ants, Pogonomyrmex spp. and Veromessor spp., cause consid-
erable damage by clearing areas of plant grov^^th near their nests. Such
individual clearings may cover areas several feet in diameter and thus
considerably reduce the crops. Some ants invade poultry houses and
attack young chicks. These same ants may also be beneficial, however,
by invading the nests of mice and rats and killing their young.

General Shape and Size of Ants. — Ants are so common that the gen-
eral shape of the body is well known. The head, thorax, and abdomen are

//(?^^

Tfyorax

ASc/o/ven

Scapff Dorsi/m

Pec//ce/

fp//7oi^/n? / I

~~ —Tarsas

Fig. 6. — Diagrammatic drawing of an ant indicating the im-
portant structures used in this circular in the description of the
different species.

sharply constricted into separate divisions. The head bears a pair of
elbowed antennae composed of a long basal segment, the scape, and a
terminal portion of several small segments, the funiculus (fig. 6) . Some-
times the small segments of the funiculus are enlarged to form, at the
extreme end of the antennae, a "funicular club" composed of one to four
segments. Ants use their antennae constantly as "feelers," their olfactory
organs being located primarily in the terminal segments. The eyes of
ants are, in general, poorly developed. The worker and male castes have
a pair of compound eyes, while the females have, in addition, three
simple eyes or ocelli located on the top of the head (fig. 7). The thorax
may be either long and slender or robust and is divided sharply into
several immovable sections. Probably the most distinctive feature of
the ant body is the manner in which the abdomen is attached to the
thorax. The attachment generally consists of one or two slender seg-

CiR. 342] Ants and Their Control 5

ments, either round or bearing- an erect or inclined projection or scale.
This petiole or pedicel is a part of the abdomen, the remainder of which
is known as the gaster. In some genera of ants the gaster is character-
istically constricted behind the first segment. Another portion of the
body often used to distinguish various forms of ants is the epinotum, the
segment to which the petiole is attached. This segment may be rounded
or may have a pyramidlike projection.

Ants within the same species vary considerably in form, the variations
not being limited to three distinct castes ; each caste may be represented
by one or more different forms. In some species the males are smaller

Fig. 7. — Head of the Argentine ant, :;-;/.

showing the characteristic arrangement
of the teeth and the elbowed antennae.
The small eyes at the top of the head
distinguish the queen from the worker.
(From Bui. 207.)

than the workers, but more commonly are larger and have specialized
mandibles. The queens are generally larger than the workers or males,
but here again dwarfs and workerlike queens are represented in certain
species. The workers, however, are more variable than the sexual forms,
the size at times depending presumably on the amount of food received
during their developmental period. Their heads vary greatly in size and
shape, determined by the functions they are to perform in the social life
of the colony. The head and mandibles of the soldier caste are very large,
whereas the head of the typical worker is small, with variations in size
between the two extremes. The head of a queen ant is usually small,
while the thorax is larger than in the other castes of the same species.

Ants are generally wingless except at mating time, when swarms of
winged males and females that have recently emerged may be seen.
After mating, the males soon die, whereas the females start separate
colonies by their own efforts or with the aid of a few workers of the same
species. The queens lose their wings soon after the nuptial flight.

6 University op California — Experiment Station

Ants are often confused with the termites, which they resemble in
many respects in their general form and social habits. Termites can be
distinguished, however, by the following characteristics : Their antennae
are like an open string of beads (moniliform), and are not elbowed as in
ants. The mouth parts are fitted solely for chewing. The fore and hind
wings, when present in the mating forms, are very similar in appearance,
being long, narrow, and laid flat on the back when not in use. Tha ^ings
extend far beyond the end of the abdomen and are borne on the :K§t two
segments of the thorax. The abdomen is broadly joined to the thorax
instead of being constricted as in ants ; and it bears, posteriorly, a pair
of appendages, or cerci, which may be short or long, according to the
species. The body of a termite has a much thinner covering than that of
an ant, since the termite does not live under exposed conditions. Most
termites are blind or have at best only vestiges of eyes. Their bodies may
be either white or black, according to the form and the species.

Food and Nesting Habits. — The feeding habits of ants differ widely
in the different species. Some depend solely on the bodies of insects or of
smaller animals they can find or destroy. Some prey on other ants, and
this habit has probably induced the practice of slave-making, typical of
certain species. Many feed on the sweet exudations of plants or the
saccharine excreta of insects; others on vegetable matter, seeds, and
even fungi. One tribe of ants cultivate fungi in special chambers under-
ground known as fungus gardens and tend the growing plants, and thus
raise their own food supply.

The harvester ants gather seeds and stems of plants and carry them
to their nests, which generally consist of fairly large mounds of soil and
castoff material in the center of a cleared area. The tunnels of some
species of ants may extend for some distance in the soil and many branch
into galleries with small chambers in which the brood is reared. Many
species construct simple nests under stones and logs, beneath the bark
of trees, or in the foundations and walls of buildings. Temperature,
moisture, and proximity to food supplies appear to be the chief factors
controlling the selection of a nesting place for most ants.

IDENTIFICATION OF SPECIES OF ANTS

For the convenience of those readers who are technically trained in pest
control, the following key is included for the identification of twenty-six
of the more important ants in California which may be termed as noxious
forms or which may be confused with them. The descriptions apply only
to worker forms unless stated otherwise. Because of the very small size
of most ants a strong hand lens or microscope will be needed in the use
of this key. A 5-centimeter scale, as an aid in identifying ants, appears at

CiR- 342] Ants and Their Control 7

the head of this key. If the species is determined accurately, one can then
select the appropriate control measures described herein by studying
the food and nesting habits of the offending species. The more noxious
forms, together with some of their habits and distribution, are further
described in the text along with the control measures.

When there is occasion to send ants for identification they are best
sent in vials containing a 70 per cent solution of alcohol. Dry specimens
should be enclosed in a small box or bottle containing some tissue paper,
the latter preventing the ants from being broken in transit. The ants
should never be mailed in envelopes, for then they become badly crushed
and difficult to classify.

Key to the Ants Discussed in This Circular

1

z

5

4

5

1. Ants with 1 segment in the pedicel (fig. 1) 2

Ants with 2 segments in the pedicel (fig. 15) 15

2. Anal opening terminal, circular, and surrounded by a fringe of hairs (fig. 25) . . 3
Anal opening not terminal, but ventral, slit-shaped, and not surrounded by a

definite fringe of hairs 10

3. Workers for the most part 2-3 mm in length 4

Workers larger than 3 mm 5

4. Thorax very narrow; gaster broader at the base (fig. 24) and coming to a sharp

point. Prenolepis imparls var. calif ornica Wheeler.
Thorax broader, not as above. Lasius niger var. neoniger Wheeler.

5. Workers for the most part smaller than 7 mm 6

Workers for the most part larger than 7 mm 7

6. Thorax and the head below the eyes distinctly rusty reddish; vertex (top) of

head and abdomen black. Formica rufibarMs var. occidua Wheeler.
Thorax not distinct in color from the abdomen but blending with abdomen.
Formica cinerea Mayr., and its subspecies and varieties.

7. Head, thorax, and abdomen black 8

Thorax reddish or yellow 9

8. Legs, except tarsi, black. Camponotus levigatus (F. Smith). Legs red. Cam-

ponotus herculeanus var. modoc Wheeler.

9. Thorax reddish ; abdomen black. Camponotus maculatus vicinus Mayr., and its

varieties.
Thorax yellowish; first and second segments near pedicel usually yellowlike
thorax. Camponotus maculatus maccooTci Forel.

10. Epinotum with a pyramidlike projection (fig. 14) 11

Epinotum without a pyramidlike projection 12

11. Head and thorax blackish, blending with the dark abdomen. Dorymyrmex

pyramicus Eoger.
Head and thorax reddish; thorax definitely different from the black abdomen.
Dorymyrmex pyramicus var. hicolor Wheeler.

8 University of California — Experiment Station

12. Larger than 2.5 mm.

Thorax reddish; head reddish black; abdomen black and velvety. Liometo-

pum apiculatum occidentale Emery.
Almost always smaller than 2.5 mm 13

13. Petiole difficult to see, lying somewhat in a horizontal position and appressed

closely against the overhanging abdomen (fig. 11). Tapinoma sessile Say.
Petiole erect (fig. 1) 14

14. Brown, no odor on being crushed ; walk in definite trails. Iridomyrmex humilis

Mayr.
Yellowish brown, lighter than above, definite odor; do not walk in definite
trails. Iridomyrmex analis (Ern. Andre).

15. Very small ants, generally less than 1.75 mm 16

Ants always larger than 1.75 mm 18

16. Antennae with 2-segmented club (fig. 16) ; red. Solenopsis molesta (Say), and

its western variety validiuscula Emery.
Antennae with 3-segmented club (fig. 18) 17

17. Eed. Monomorium pharaonis (Linn.).
Black. Monomorium minimum Buckley.

18. Pedicel inserted dorsally on abdomen (fig. 22).

Abdomen heart-shaped, flattened dorsally, curved ventrally, and coming to a

sharp point. Crematogaster sp.
Pedicel inserted terminally on abdomen (fig. 20) 19

19. Antennae 11-jointed.

Pair of spines on head; thorax with 3 pairs of dorsal spines or tubercles.

Atta versicolor Pergande.
Antennae not 11-jointed 20

20. Antennae 10-jointed.

Antennae with a 2-segmented club (fig. 16) ; head and thorax shining red;

abdomen black. Solenopsis xyloni var. maniosa Wheeler.
Antennae 12-jointed; antennal club, when present, with more than 2 joints.

21. Antennae with a 3-jointed club (fig. 21).

Head with a deep furrow on vertex (fig. 21). Pheidole sp.

Antennae without a 3-jointed club 22

22. Smaller than 3.5 mm. Blackish in color. Tetramorium caespitum (Linn.).
Larger than 3.5 mm 23

23. Dorsum with a suture (fig. 20) 24

Dorsum without a suture 25

24. Thorax and petiole brownish; abdomen black. Veromessor andrei (Mayr.).
Thorax, petiole, and abdomen all shining black. Veromessor pergandei (Mayr.).

25. Posterior part of thorax without a pair of spines ; bright red. Pogonomyrmex

calif ornicus Buckley, and its subspecies and varieties.
Posterior part of thorax with a pair of small spines ; dark red. Pogonomyrmex
suhdentatus Mayr.

CONTROL MEASURES

General Considerations. — A stud}^ of the feeding and nesting habits of
noxious ants aids one materially in selecting the measures needed for
their control. Since queen ants are very prolific and give rise to an ever

CiR. 342] Ants and Their Control 9

increasing horde to replace those that die through natural causes or are
killed by accident or by designs of man, ultimate control must include
the destruction of the queens rather than the more simple elimination of
the offending workers. To accomplish this end, one must seek out the
nests and apply such remedies as poisonous gases, solutions and powders ;
or use poisoned baits that will destroy the ants and their queens when
brought to them by the workers. The innumerable places in which ants
may build, the intricate architecture of some of their nests, their diverse
food habits, and the facility with which they move their brood and queens
to more favorable locations on the first approach of danger often make
this task very difficult indeed.

Another factor that greatly hampers control is the ease with which
ants may be spread from one location to another through the transporta-
tion of their nests or queens in nursery stock, manure, sod, or lumber,
and by a variety of other means. Ants of themselves do not spread very
rapidly, a factor that should facilitate their control.

The control measures for noxious ants may be divided into four gen-
eral groups, based somewhat upon the food and nesting habits of the
offending species. Many of the proprietary compounds that have been
found satisfactory in the control of ants fit into one or more of these
control divisions.

Precautions. — Since most of the poisons used in controlling ants are
deadly to other creatures as well, they must he kept away from children
and domestic animals. Keep all poisons properly labeled. A list of anti-
dotes and emetics is given at the end of this circular for use in case
poisons mentioned herein are taken accidentally.

Prevention and Repellents. — Measures that will prevent ants from
having access to food materials or to nesting places where they will be
difficult to control are to be recommended. Food in the kitchen and
pantry should be kept in tightly covered containers, while drainboards
and sinks should be kept free of food attractive to scouting ants that are
forever looking for a new supply. Ants may be kept from exposed food
by surrounding the latter with water in a larger receptacle. The legs of
tables and ice boxes may be placed in tins partially filled with water or
light oil. Food boxes may also be suspended by wires protected by tangle-
foot preparations or by repellents. Constant vigilance is necessary even
under these conditions to keep ants from walking over dust-laden sur-
faces of such repellent materials.

Colonies of bees may be protected from ants by placing the hives on
stands with the legs in cans partially filled with a light oil. Sometimes
inverted metal cones are tacked to the legs of such a stand, and the sur-

10 University of California — Experiment Station

faces of the cones are painted with tanglefoot, renewed as necessary.
Poison bait in ant tins placed in the vicinity of the hives will keep down
the ant population where the nests cannot be found and destroyed, but
care must be exercised to have the holes in the cans small enough to keep
bees from gaining access to such poisons. Saturating the ground beneath
the hives with crankcase oil discourages ants from building there.
Carbolic acid solutions should not be used around beehives for control-
ling ants, for they are repellent to bees.

Sometimes ants gain access to dwellings by climbing trees or shrub-
bery in contact with the roofs or walls. Such invasions can be stopped by
pruning back the branches and by setting out appropriate poison baits
near the ant trails. (See "Repellents," page 31.)

Contact Insecticides. — To eliminate an invasion of ants temporarily
it is sometimes expedient to use oily or corrosive sprays that kill the
ants when brought in contact with their bodies. These measures afford
temporary relief only ; they have no lasting effect on the colony popula-
tion. They are most effective at swarming time, when many queens may
be killed by spraying. (See "Contact Insecticides," page 32.)

Fumigants. — Where fumigants can be introduced into ant nests with-
out endangering other animal life or growing plants, an efficient appli-
cation will exterminate the entire population, including the queens
and developing stages. This is the only positive means of eradication. It
kills the colony at its source — the queens ; and the workers that are not
killed will soon die. (See "Fumigants," pages 32-33.)

Stomach Poisons. — These poisons are generally used in two different
media : in sugar sirup and honey for sweet-loving ants and in grease or
fats for fat-loving ants. The ideal poison is one that will either kill or
affect the workers so slowly that they will carry it into their nests to
poison the queens and brood. Most poison baits, however, simply reduce
the populations temporarily and then must be used again periodically
when the colony strength is regenerated. (See "Stomach Poisons," pages
33-35.)

DESCRIPTION AND CONTROL OF THE COMMONER ANTS
IN CALIFORNIA

THE ARGENTINE ANT, IRIDOMYRMEX HUMHiIS MAYR.

General Distribution. — The Argentine ant, first observed in New Orleans
in 1891, was supposed to have been introduced on coffee ships arriving
from Brazil. It has been spread rapidly by various agencies of man
throughout the southern states. It was first collected in California in
1905, probably near Ontario, by E. S. G. Titus. In 1908, after the identi-

Cm. 342]

Ants and Their Control

11

fication of this pest was definitely determined, colonies were fonnd estab-
lished at Alameda, East Oakland, San Francisco, San Jose, and at a
point near Campbell; and in sonthern (California it was located by Pro-
fessor H. J. Qnayle in Los Angeles, Azusa, and Upland. By 1910 it had
occupied about 5,000 acres in the state and by 1916 had become estab-
lished in 16 separate localities. Since then the Argentine ant has'become

Fig. 8. — Worker of Iridomyrmex analis. (From Bui. 207.)

generally established throughout California at the lower altitudes in
moist situations around residences and in orchards. The cost of control-
ling this pernicious species is continually mounting, as is the amount of
damage attributed to it.

Description. — The workers of the Argentine ant (fig. 1) are 2.2 to
2.6 mm (millimeters) in length when the abdomen is not distended with
food. They are brown, with the thorax, scapes, and legs somewhat lighter.
The mandibles are yellowish and characteristically dentate (fig. 7). The
queens are larger and more robust than the males. No perceptible odor
is produced on crushing individual specimens of this ant, but when large
numbers are crushed, a characteristic musty or greasy odor is noticeable.
This ant always works in definite trails.

The Argentine ant is often confused with the odorous house ant,
Tapinoma sessile, also a common, sweet-devouring household pest that
moves in trails. The odorous house ant is blacker, slower, and more squat,
with a broader abdomen ; upon being crushed it gives forth a pungent
odor, usually lacking in the Argentine ant. Another ant, Iridomyrmex
analis (fig. 8) closely resembles the Argentine in structure; it differs,
however, in being much paler-colored, having a noticeable odor, and not
confining its foraging to distinct trails.

Nesting Hahits. — Nests of the Argentine ant are situated wherever

12 University op California — Experiment Station

sufficient moisture is available and wherever light is excluded, both in-
side the house and outside in the garden or orchard. Within the nest are
numerous queens that show no antagonism to one another. Mating takes
place in the nest and nuptial flights are as rare as are the winged females.
The queens are very prolific, laying eggs in enormous numbers. The rate
of egg production and the time necessary for the completion of the egg,
larval, and pupal stages all vary greatly with temperature, moisture,
nutrition, and other factors. The time from the egg to the adult has been
observed to vary from 33 to 141 days, with an average of 74 days.

In California these ants begin to increase toward the end of February,
reach their maximum numbers during July, August, and September,
and decrease about the middle of October. During the winter they con-
gregate and form large colonies in limited areas, the favorite nesting
places being under hedges in leaf accumulations ; in the ground, where
they penetrate to a depth of 6 inches ; and in manholes or basements kept
warm by steam pipes. Hundreds of queens may be present in such
localized colonies. During the spring and summer the ants gradually
spread out over larger areas, particularly along the edges of walks,
under shrubbery, and in other situations kept well moistened. At such
times the nests are usually from % to 1^ inches below the surface of
the soil.

Argentine ants are a nuisance in the household because they invade
the cupboard and intermingle with all the provisions therein, being par-
ticularly fond of such sweets as sugar, honey, and cake.

In the garden and orchard they faithfully tend and protect such
"ant-cows" as plant lice, mealybugs, and scale insects for the honeydew
excreted by these insects. Since the ants effectively force parasites and
predators of these insects to keep their distance, the "ant-cows" increase
beyond their normal numbers and greatly injure the vegetation on
which they feed. The control of plant lice, mealybugs, and scale insects,
therefore, is directly involved in the control of their efficient bodyguards,
the Argentine ants.

Control. — The Argentine ant can be reduced or exterminated only
through continuous and unrelenting efforts that match the ants in per-
sistence. As stated previously, control should be directed against the
queens, for relief can be expected only where the queens are either
exterminated or greatly reduced in numbers. As many observers have
noted, control is easiest in the spring or autumn, the problem being
somewhat more difficult during midsummer because then the colonies
are stronger and more scattered and because the honeydew of plant lice,
mealybugs, and coccids acts as a counter attraction to the poison baits.

CiR. 342] Ants and Their Control 13

One may definitely control the Argentine ant by pouring carbon di-
sulfide* (page 32), cyanide" (pages 32-33), kerosene-pyrethrum (for-
mula 3) or kerosene (page 32) into their nests after first perforating
the latter with a pointed implement. A solution of pyrethrum and soap
(formula 7) should be used where vegetation is abundant. The direct
application of fluids is usually feasible only in small areas, as around
the foundations of a house and in the garden, since the nests are usually
small, numerous, and hard to find. As the Argentine ant prefers situa-
tions where leaves have accumulated, leaf debris must be removed.

At times, particularly during the summer, when the ants are widely
distributed throughout an infested area, direct application of liquids
may not be feasible. Recourse must then be made to sweetened poison
baits upon which the ants will feed and which they will later carry to
the queens and the larvae in the nest. Thus through the slow poisoning
of the workers, queens, and young, effective control may be realized in
a relatively short time.

The government Argentine ant formula (formula 8) and the modified
ant sirup (formula 9) are effective in controlling this ant. Sodium arsen-
ite is a deadly poison and when used, should always be placed outside
dwellings, and away from small children and domestic animals. The
poison baits should be put in suitable receptacles, containing several
strands of excelsior, and then placed near the ant trails. Cans should be
distributed every few feet, particularly near the foundation of the
house or in the orchard where the trails of ants are most commonly
found. These cans should be refilled with poison sirup every 5 to 10 days.
Since in time the sirup may harden through evaporation and become
unattractive to the ants, the cans should be cleaned and the excelsior
replaced every 3 or 4 weeks. All the cans should be set out at one time so
that the effect of the poison on the ants will be intensified as quickly as
possible. The speed and the effectiveness with which the ants are con-
trolled often depend upon the number of cans distributed.

If, after 2 to 5 days, the number of ants dwindles, if a great many dead
ants are seen lying in the vicinity of the cans, if other than Argentine
ants begin to forage at the cans, and if sick queens are dragged about by
the workers, then control is under way and the poison bait should be
replenished.

Often the ants will make their shallow and loose, earthy nests directly

* Carbon disulfide is highly explosive when brought in contact with a flame.

^ Cyanide is an extremely poisonous compound and particular care should be exer-
cised to prevent any person or domestic animal from breathing its fumes or getting
it into the mouth.

14 University of California — Experiment Station

under the cans ; if this happens, the cans should be moved to different
locations and such nest sites vv^etted v^ith kerosene or any other soil in-
secticide.

Only rarely are all the queens exterminated ; therefore the ants, after
2 to 6 months, may multiply to their former numbers. There is little like-
lihood of this occurring if the cans are kept filled with poison.

It is advisable to move the cans — if only a few feet — about once a
month, for should the ants become sick, they may not return to cans
situated in the same place.

Whenever the ants are found nesting- in cracks inside a house, cotton
wads saturated with a mixture of ethylene-dichloride and carbon-tetra-
chloride (formula 6) , or with the kerosene and pyrethrum mixture (for-
mula 3) or with kerosene alone, and inserted in several places along the
fissure, will often force the ants to leave. An atomizer or oil can may be
used to force these materials into the crevices. Ordinary fly spray is
useful for the prompt extermination of ants entering the house.

Chemicals like pyrethrum, sodium fluoride, naphthalene, and paradi-
chlorobenzene may be spread about where the ants are passing; these
materials are not, as a rule, very effective against the Argentine ant.
Nicotine sulfate as a spray on plants often repels ants in general.

Tartar emetic sirup (formula 12) is not very effective against the
Argentine ant, being slow in its action, but it may bring some control
after 5 or 6 weeks. The use of tartar emetic placed in cans is advisable in
dairies, groceries, and other places where food is merchandised. One may
control the ants entering such establishments by distributing poison
baits outside the building.

Where ants are to be controlled over large areas (for example on
school grounds) where there are many buildings, and where the number
of cans and the amount of labor to be expended is limited, the cans,
instead of being widely distributed, should be concentrated about the
chief source of infestation ; and by intensifying the poison campaign at
this point, one is often able to control the pest. Then the cans should be
moved on to the next center, and the campaign concentrated there in a
like manner.

Control in orchards may be effected with the Argentine ant formula
(formulas 8 or 9) . Four-ounce baking powder tins (fig. 9, Z>) , with oppo-
site sides indented to permit the entrance of ants, can be used for this
purpose. About two cans should be distributed to the acre, attached to
pointed stakes 2 feet long that are driven into the ground. A piece of
board nailed over the end of each stake will shade the can and decrease
evaporation of its contents.

CiR. 342]

Ants and Their Control

15

D

Fig. 9. — A, B, A method of making the lids of cans fast so that children cannot
readily remove them ; C, a wire stake that may be used to fasten cans to the ground ;
D, an ordinary baking powder tin with an indented side makes an excellent poison can.

16

University of California — Experiment Station

Because of the danger of children or animals overturning the cans, the
cans and lids should be attached by some such means as shown in figure
9, A, B, and C, and located as inconspicuously as possible. A method of
making the lids of cans difficult to remove is as follows : a piece of wire
is passed through two small holes in the lid to form a closed loop (fig.

Fig. 10. — Face of the odorous house ant.
This species of ant is most commonly confused
with the Argentine ant. Note particularly the
arrangement of the teeth on the jaws. (From
Bui. 207.)

Fig. 11. — Worker of the odorous house ant. Note how the top of
the abdomen overhangs the "hump." (From Bui. 207.)

9, A) ; holes are bored through the can on opposite sides so that a screw
can be passed through it with the wire from the lid under the screw
(fig. 9, B) ; and the screw is then inserted into a stake, wall, or tree.

Poison cans should be waterproofed with paraffin of a high melting
point (above 124° F). In each 4-ounce paraffined can (fig. 9, D) a few
loose strands of excelsior are placed, and then the sirup is poured in

CiR. 342] Ants and Their Control 17

until the container is one-third to one-half full. Before being paraffined
the cans should have a hole punched in them near the top of one side, by
means of which the can may be nailed to the tree or stake preferably
where the ants are most numerous.

THE ODOROUS HOUSE ANT, TAPINOMA SESSILE SAY

This small black ant (figs. 10 and 11) is distributed throughout the
United States from sea level to 10,000 feet and ranks second only to the
Argentine ant as a house pest. It is 2-3 mm long and may be readily dis-
tinguished from the Argentine ant (which it superficially resembles)

Fig. 12. — Worker of the California velvety tree ant.

by its darker color, by its odor upon being crushed, and by the fact that
the overhanging abdomen apparently hides the petiole, which is readily
seen in the Argentine ant. This sweet-loving ant travels in trails, often
invades the kitchen, and may be found nesting in crevices between the
walls, sills, or floors. In the orchard it is fairly important because of its
habit of tending plant lice. It commonly occurs in apiaries, where large
colonies often may be found beneath the top and inner covers of a hive.
There, however, it is apparently of little consequence, for it nests in the
hive apparently because of the warmth given oif by the colony rather
than because of proximity to a food supply.

Control may be accomplished by methods listed for the Argentine ant.

THE CALIFORNIA VELVETY TREE ANT, LIOMETOPUM APICULATUM
OCCIDENTALE EMERY

The worker of this ant (fig. 12) is 2.5 to 6 mm in length, with a glistening
velvety-black abdomen, a red thorax, and a brownish-black head. These
ants are found in the foothills and mountains throughout the state. They
are exceedingly common in the San Joaquin and Sacramento valleys,

18

University of California — Experiment Station

where they range up and down oak, alder, elm, and other trees in order
to tend plant lice. Their trails may extend many feet from the base of
the tree or log where they nest. Houses are subject to invasion not only
for sweets but also for insects. The ants generaly make their forays in

Fig. 13. — Head of Dorymyrmex
pyramicus. The coarse teeth on
the jaws are very characteristic
of this ant. (From Bui. 207.)

Fig. 14. — Worker of Dorymyrmex pyramicus. Notice the pyramid
above the base of the middle and hind legs. (From Bui. 207.)

dwellings at dusk or during nighttime, although many searchers may
be present during daylight hours. The queens have been found nesting
beneath rocks and fallen timber.

Control may be secured by placing five or six cans containing the
Argentine ant poison (formula 8 or 9) at the base of each tree or post
where ants occur in the greatest numbers. Although this poison kills
rather slowly, it more or less limits the forays to the vicinity of the cans.

^'iR- 342] Ants and Their Control 19

A mixture of pyrethrum and sodium fluoride (formula 11) distributed
around the base of the tree at the rate of % pound per tree will effec-
tively keep them from climbing thereon for about 5 days; and not only
will this mixture kill many of the ants, but it will often force them to
move their nests elsewhere. The powder should completely encircle the
base of the tree, and some of it should be sifted a foot or more up the
trunk. This mixture may kill all the vegetation to a distance of 6 inches
from the tree base. After 5 days the powder will have to be renewed.
Tree surgery to remove decayed portions in which the ants nest will aid
in eliminating this pest.

THE PYRAMID ANT, DORYMYRMEX PYRAMICUS ROGER

This ant is relatively common at the lower altitudes throughout Cali-
fornia. It is small, 1.5 to 2.0 mm in length, with a reddish-black head and
thorax and a black abdomen. The head features and the pyramidlike
projection on the thorax are distinctive (figs. 13 and 14). It nests pre-
dominantly in dry, vegetation-free areas. In southern California it some-
times invades dwellings.

Best control is obtained with such soil fumigants as kerosene, carbon
disulfide or a mixture of kerosene and pyrethrum (formula 3) poured
into nests in the manner previously described for the Argentine ant.
Poison sirups are also effective.

THE BICOLORED PYRAMID ANT, DORYMYRMEX PYRAMICUS
VAR. BICOLOR WHEELER

This ant, slightly larger than the pyramid ant, has a red head and
thorax. In habits and distribution it resembles the pyramid ant. It is of
negligible economic importance.

THE CALIFORNIA (MEXICAN) FIRE ANT, SOLENOPSIS XYLONI
VAR. MANIOSA WHEELER

Description. — This, one of the most serious ant pests in California, is
distributed at lower altitudes from southern California up through the
Sacramento Valley. The worker (figs. 15 and 16) is 1.6 to 5.8 mm in
length, with a yellowish-red head and thorax and a black abdomen. The
females are about 6.6 mm in length, light reddish brown with a black
abdomen; the males are reddish black with reddish-yellow legs. The
males and females may be observed throughout the year, particularly
on warm days, moving actively on the surface of the ground, most com-
monly from June to September. These winged forms are often observed
in enormous numbers in store windows.

20

University of California — Experiment Station

The California fire ant is the only common fire ant known to occur in
California; it is generally distributed throughout Arizona and New
Mexico. In the field these ants dwell beneath boards and stones and in
fissures in the soil as well as in cracks in sidewalks, where they generally

Fig. 15. — Worker of the California fire ant. The small figures
shoAv the difference in size between the largest and smallest workers
of this ant. (From Bui. 207.)

Fig.16, — Head of the California fire
ant. The 2-segmented antennal club is
characteristic of this species. (From
Bui. 207.)

construct flattened and irregular craters of thrown-up soil. When dis-
turbed by other ants they raise and vibrate their abdomens peculiarly.
Being very pugnacious, they will rush from the nest and bite and sting
upon the slightest provocation. They are important pests because they
invade houses, steal seeds, feed upon plants in both greenhouses and
orchards, tend plant lice and mealybugs, feed on fatty foods, and gnaw
holes in clothing. Their sting causes a burning sensation, hence the name
"fire ant." They frequently destroy almonds that have fallen to the

CiR. 342] Ants and Their Control 21

ground. In citrus orchards they are known to remove bark from young
trees and to feed upon the cambium layer.

Control. — These ants may be controlled over small areas by pouring
kerosene, or carbon disulphide, into their nests. They may be effectively
controlled in lawns by sprinkling a liberal amount of pyrethrum over
the nest and covering the area to confine the fumes.

Control in orchards and greenhouses is sometimes effected through the
use of sodium arsenite sirup (formula 8 or 9). One or two grams of

Fig. 17. — Worker of the western thief ant. This tiny ant is very often
an important pest in the home.

powdered arsenic, however, thoroughly mixed with 100 grams of
ground-up walnut meats or rubbed into bacon strips (formula 10) has
often been effective. When these ants invade the kitchen and feed on
cereals, their numbers may be reduced by preparing a poison using 100
grams of the cereal to 1 or 2 grams of sodium arsenite. This bait should
be placed in appropriately labeled ant tins where the ants occur. In such
cases the nests of these ants will generally be found in the ground outside
the house. Calcium cyanide applied to the nest is very effective. The dust
should be laid down in a thin layer over the surface of the soil and cov-
ered with a board ; it should not be mixed with the soil if the nest is 5 feet
or less from the base of the tree. Other soil fumigants may be used as
listed under Argentine ant control.

THE WESTERN THIEF ANT, SOLENOPSIS MOLESTA
VAR. VALIDIUSCULA EMERY

These tiny yellowish ants (fig. 17) are approximately 1 to 1.5 mm long.
They may be distinguished from Pharaoh's ant, which they superficially
resemble, by their smaller size, by their lighter color, and by the anten-
nae having a two-jointed club rather than a three-jointed club.

22

University of California — Experiment Station

Although, in the West, these ants normally live in the fields, they may
invade and nest in or under houses, where they become pests of great
importance. Sweets do not attract them ; they are usually found feeding
on grease, other animal matter, and cheese. Often they feed upon dead
rats and mice, and thus might convey disease-producing organisms to
human food. They are a source of great trouble in poultry houses, where

Fig. 18. — Head of Monomorium
sp. This tiny ant is often a house-
invading ant. (From Bui. 207.)

they attack young chicks. Because of their small size they are not easily
kept from any container in which food is stored.

Control. — Effective control has been obtained by using bacon strips
into which a small quantity of arsenic (about a pinch) has been rubbed
thoroughly (formula 10). The bacon is then distributed in ant cans. It
should never be exposed where animals and children might get it. Such
materials as powdered derris, fresh pyrethrum, or a mixture of sodium
fluoride and pyrethrum (formula 11) , spread near the source of infesta-
tion, will often repel or kill these ants. Care must be used in the handling
of sodium fluoride as this compound is too poisonous to be distributed
haphazardly in the kitchen.

Since these ants nearly alw^ays nest in crevices, liquid materials such
as kerosene, a mixture of kerosene and pyrethrum (formula 3), or a
solution made of ethylene dichloride and carbon tetrachloride (formula
6 ) , may be put into the crevices by means of cotton wadding or injected
with a syringe or oilcan.

PHARAOH'S ANT OR THE LITTLE RED ANT, MONOMORIUM
PHARAONIS (LINN.)

Pharaoh's ant is light yellow in color and about 1.5 mm long. Its nests
are to be found in crevices in the walls and floors of the house as well as
in the garden or lawn. Each nest usually contains two or three very fer-

CiR. 342] Ants and Their Control 23

tile queens, which, in heated houses, may breed throughout the year.
These ants are not so common in the West as in the East. They feed
readily on sweets and are particularly fond of greasy materials. They
may be distinguished from the thief ant by the three segments in the
antennal club (fig. 18) as compared with the two-segmented antennal
club of the thief ant. The thief ant, furthermore, confines itself more
closely to greases in its feeding.

Control. — A mixture of sodium fluoride and pyrethrum (formula 11)
has successfully controlled the Pharaoh's ant ; the material is scattered
where the ants occur most commonly. Powdered derris and sodium
fluosilicate also prove effective when scattered in dust form. These ma-
terials are poisonous to ants and retain their repelling effect for several
days. A pinch of sodium arsenite rubbed into bacon strips may be used
as a control for them as for the western thief ant. Ants in crevices may
be controlled by the same fumigants as listed for the western thief ant.

THE TINY BLACK ANT, MONOMORIUM MINIMUM BUCKLEY

This jet-black ant is slightly smaller than Pharaoh's ant, being but 1 to
1.5 mm long. It is distributed throughout the United States. The nests
are often found beneath rocks, in lawns, or in areas free of vegetation,
where their presence is betrayed by the very tiny craters of fine soil.
Though not nearly so much a house ant as Pharaoh's ant, the tiny black
ant does often invade dwellings in search of sweets and greases. The con-
trol methods listed for the Pharaoh's ant may be used for this species.

THE AGRICULTURAL OR HARVESTER ANTS OF THE GENUS
POGONOMYRMEX

California has a number of agricultural ants, sometimes important be-
cause they clear large areas of plant growth about their nests. Also when
disturbed near their nests, these ants sting viciously. They inhabit chiefly
arid areas. The long hairs (fig. 19) which extend from the so-called
"chins" of these ants and their reddish color are characteristic of both
species.

The California agricultural ant, Pogonomyrmex calif ornicus Buckley,
is the most common agricultural ant in California. It is from 5.5 to 6 mm
in length with the body color a light rusty red, the mandibles, clypeus,
and legs being more yellowish. There are no spines on the thorax.

The small-toothed agricultural ant, Pogonomyrmex suhdentatus
Mayr., widely distributed throughout California, is an attractively col-
ored ant about 6 mm in length of a dark wine-red color. It is rarely of
economic importance.

24

University of California — Experiment Station

Control. — Carbon disulfide has been successful in the control of the
agricultural ant. About 4 ounces is applied to each nest in one of the
following ways :

1. Expose the several tunnels of the nest by removing the top layer of
soil to a depth of about 6 inches, pour carbon disulfide in the tunnels and
over the surface of the ground, and replace the soil.

2. Pour the liquid directly in the exposed entrances without disturb-
ing the nests ; then cover the holes with earth.

3. Pour the carbon disulfide into a shallow pan on top of the nest, and
cover the entire mound with a metal tub or wet canvas, the edges of

Fig. 19. — Worker of the California agricultural ant,
Pogonomyrmex californicus. These ants often coil them-
selves up as shown, when picked up. Note the long hairs
on the underside of the head. (From Bui. 207.)

which should be banked with earth. Cover with soil any portion of the
nest not covered by the tub or canvas.

For better results, repeat the application after one week. Because of
the fierceness with which these ants sting, boots should be worn while
digging around the nests.

THE AGRICULTURAL OR HARVESTER ANTS OF THE GENUS
VEROMESSOR

The black harvester ant, Veromessor andrei (Mayr.), shown in figure 20
is 4.5 to 7 mm in length, with a reddish-black thorax ; in some specimens
the posterior part of the abdomen is black. This ant is almost entirely
limited to California in its distribution, being most common in the south-
ern part of the state.

Cm. 342] Ants and Their Control 25

The jet-black harvester ant, Veromessor pergandei (Mayr.), 2.5 to 6
mm in length, occurs throughout the arid portions of the Southwest but
in California is limited to the southern part of the state.

Having habits somewhat similar to those of the California agricul-
tural ant, these ants may be controlled by similar methods.

Fig. 20. — Worker of a black harvester ant, Veromessor andrei.
Note the position of the thoracic spines (only one of which is
shown )and that the pedicel is attached terminally. (From Bui. 207.)

THE PAVEMENT ANT, TETRAMORIUM CAESPITUM (LINN.)

The pavement ant is a small blackish-brown ant some 2 to 3 mm in length
with pale legs and antennae and with a black abdomen. The head and
thorax are furrowed by parallel lines. A pair of small spines adorn the
posterior portion of the thorax. Hairs are thickly distributed over the
entire body.

The pavement ant is a European meadow ant distributed in the
United States along the Atlantic seaboard and in the Middle West. In
California it is distributed in the Sacramento Valley and is a potential
household nuisance. It is to be found under pavements, under stones, and
in lawns, from which vantage points it may range into households, where
it becomes a pest.

This slow-moving ant may be destroyed by measures recommended for
the Argentine ant.

THE BIG-HEADED ANT, PHEIDOLE SPP.

Ants of the genus Pheidole (fig. 21) live in situations somewhat similar
to those inhabited by fire ants and are distributed throughout the warmer
areas of the United States. Although superficially similar to the fire ants,
they may be distinguished from the latter by their 12-jointed antennae

26 University op California — Experiment Station

and 3-jointed antennal club. At times they may cause annoyance in seed-
beds and also in houses.

This ant may be controlled by methods recommended for the Cali-
fornia fire ant. Hamlin® found that Pheidole hyaiti Emery could be
effectively kept from refrigerators by standing the castors in small
metal pans filled with a dry mixture of whiting and flowers of sulfur in
approximately equal proportions. The pans were 4 inches in diameter
and 11/2 inches deep. The repellent quality, of the powder will endure
for a long period if the mixture is not moistened.

Fig. 21. — Head of Pheidole hyatti.
This ant occasionally becomes a house-
invading pest in the vicinity of Fresno.

THE LEAF-CUTTING ANT, ATTA VERSICOLOR PERGANDE

Only one species of the leaf-cutting, fungus-growing ant of the genus
Atta is reported from California. It is a terrible scourge in the warmer
parts of North and South America, but fortunately is rare in California
and is of no economic consequence here.

THE ACROBAT ANT, CREMATOGASTER SPP.

The acrobat ants (figs. 22 and 23) may be recognized by the heart-shaped
abdomen, flattened on the upper surface and curved below. They are
widely distributed throughout the country and in California are often
found under rocks. Their movements are slow and they have a peculiar
habit of raising the abdomen over the head and thorax which has given
rise to the name "acrobat." These ants tend plant lice and are known to
construct small "cowsheds" of vegetable fragments or earth as covers
over aphids and coccids. They have little economic importance and may
be controlled by the measures recommended for the Argentine ant.

^ Hamlin, J. C. Inexpensive method of protecting household refrigerators from
ants. Jour. Econ. Ent. 21:2, 431. 1928.

CiR. 342

Ants and Their Control

27

THE CALIFORNIA HONEY ANT, PRENOLEPIS IMPARIS VAR.
CALIFORNICA WHEELER

The California honey ant is brownish black (fig. 24) and has a somewhat
triangular abdomen. The worker is 2.3 to 2.5 mm in length, shiny
brownish black, with antennae and legs brown, tarsi paler and more
yellowish. It is common throughout the state and may often be found

Fig. 22. — Worker of the acrobat ant, Crematogaster sp. Notice the
shape of the abdomen, which is often held up over the thorax. (From
Bui. 207.)

Fig. 23.— Top view of the body of the acrobat ant. (From Bui. 207.)

ascending trees in the orchard. It feeds upon honeydew, an excretory
product of scale insects and plant lice, as well as upon the exudates of
young plant tissues ; and in Los Angeles County is said to devour the
tender growths of orange trees. After feeding, the abdomen of this ant
becomes greatly distended and amber in color.

This species often replaces the Argentine ant whenever the latter has
been eradicated. It may be controlled by the same methods as for that
species.

28 University of California — Experiment Station

CARPENTER ANTS, CAMPONOTUS SPP.

Carpenter ants (fig. 25) are our largest ants in California and vary
greatly in size. The workers are from 6 to 10 mm long ; the queens from
13 to 15 mm.

The maculate carpenter ant, Camponotus maculatus vicinus Mayr.,
and its varieties are large, attractive ants with a red thorax and a black
abdomen. Maccook's maculate carpenter ant, Camponotus maculatus
maccooki (Forel), though very similar to the above-mentioned species,

Fig. 24. — Worker of the California honey ant. Notice the shape
of the abdomen. (From Bui. 207.)

differs in being paler, with the thorax and the first and second segments
of the abdomen near the pedicel yellowish. The carpenter ants are rarely
injurious in California. These ants at times forage in houses. Their
presence there, however, is more or less accidental, the nests being usually
situated in the soil some distance from the house ; at times they may dis-
figure lawns with their mounds.

Control. — Where control is required and whenever the nest of this ant
can be located, destruction is possible through the use of kerosene and
pyrethrum (formula 3), pyrethrum and soap solution (formula 7), or
carbon disulfide. Plunge a sharp stick in and around the entrance to the
nest, and then pour the solution into the openings until the soil is satu-
rated. If the treatment is repeated in 3 to 6 hours, its effectiveness will
be increased.

Where the nest cannot be located, baits may be used. If these are placed
in shaded places out of doors, the ants are more likely to be attracted to
them. Tartar emetic sirup (formula 12) distributed in ant cans, has been
used effectively. The entrances to the cans should be l^ inch in diameter.

CiR. 342]

Ants and Their Control

29

The giant carpenter ant, Camponotus levigatus, an all-black ant, and
the Modoc carpenter ant, Camponotus herculeanus var. modoc, a black
ant with reddish legs, are found in the mountains of California where
they sometimes tunnel in the walls of log cabins. They may be controlled
where necessary with tartar emetic (formula 12) distributed in poison

Fig. 25. — Worker of a carpenter ant (Camponotus) .

cans. The destruction of the ants in their burrows may be effected by
injecting such fumigants as are listed under "Fumigants" on pages 32-
33. Thoroughly soaking the timbers with kerosene will often drive the
ants from their tunnels. Foundation timbers impregnated with creosote
will repel the carpenter ants. The increased fire hazards of such timbers,
however, should be taken into consideration.

FIELD ANTS, FORMICA SPP.

Medium-sized ants of the genus Formica (fig. 26) occur in the fields at
high and low altitudes everywhere in the state. Although they tend
aphids, they are as a rule fiercely predacious on insects.

The California brown field ants, Formica cinerea subspecies and varie-
ties, are 3 to 7 mm in length, have a brownish-red thorax and a somewhat
grayish abdomen. They are often found nesting in cracks in sidewalks,
in nests with many entrances along the sides of buildings, and at the
bases of trees. They may become obnoxious by foraging in houses and by
tending plant lice on trees and shrubs. These are the commonest Formica

30 University of California — Experiment Station

in California and are often observed rnnninof in long trails along- fences,
sidewalks, or bnildings.

The California red and black field ant, Formica rufiharhis var. occidua
Wheeler, is 4 to 7.5 mm in length, v^ith the thorax red, the abdomen
silvery black, and the top of the head dusky brown. This ant has approxi-

Fig. 26. — Face of the queen of a field
ant (Formica). Notice the large eyes.
(From Bui. 207.)

mately the same habits and distribution as the California brown field
ants. It has a fairly characteristic jerky method of running and stopping.

The western mound-building ant, Formica rufa ohscuripes Forel,
varies from 3.8 to 8 mm in length, with the head and thorax red and the
abdomen brownish black. It occurs at high altitudes (5,000 to 8,000 feet)
in California and the northwestern states into British Columbia. Mounds
are often constructed by this ant from small sticks, leaves, and pine
needles. Ants building mounds in forested areas are often deleterious to
seedlings and native growth adjacent. In Canada, R. C. Treherne^ states
that these ants destroy pistils in the blossoms of fruit trees in order to
reach the nectar, and thus cause considerable losses to fruit growers.

Control. — The field ants mentioned above may be controlled with the
soil fumigants listed for carpenter ants, as well as with ant sirup (for-
mulas 8 and 9).

LASIUS SPP.

Ants of the genus Lasius are often fairly important in the Middle West

because they tend aphids in the fields. In California they cause little

trouble.

They may be controlled when necessary by methods outlined for the

control of the Argentine ant.

' Treherne, R. C. Notes of economic interest from British Columbia. Can. Entom.
47:101-4. 1915.

CiR. 342] . Ants and Their Control 31

MATERIALS AND FORMULAS USED IN ANT CONTROL

As many of the materials mentioned herein are poisonous to humans and
to domestic animals, it is recommended that all formulas be mixed by
druggists in order to reduce the dangers of accidental poisoning to the
minimum.

REPELLENTS

The following materials have been used with varying degrees of success
in repelling ants :

Camphor, naphthalene flakes, paradichlorobenzene, carbolic acid
emulsions, corrosive sublimate, turpentine, coal oil, and oil of citronella.

Formula 1
Carbolic Acid Bands

Crude carbolic acid (phenol solution) 1 pint

Fish-oil soap 1 pound

Water 3 gallons

Ants often build their nests around the bases of trees, especially citrus
trees. In such situations, strong solutions of cyanide or carbon disulfide
will injure the tree. Crude carbolic acid is not very uniform. A pound of
crystals can be substituted for the crude product in the formula given
above. Though more expensive, it may be more satisfactory in the
long run.

Formula 2
Sulfur Bands

Finely pulverized sulfur 1 part by weight

Commercial "tree-sticky" or tanglefoot 6 parts by weight

The two ingredients should be mixed together thoroughly, without
heat, by use of a wooden paddle. This mixture will remain effective in
exceptionally dry, foggy, or rainy weather, under all temperatures at
whici the ants will work, for periods of from three to five months. It
appears to have a slightly repellent effect in addition to its more lasting
viscosity. It must not be applied directly to the bark, for it will be ab-
sorbed to some extent and in time will injure the tree. The trunk should
first be wound with hose-mending tape, or with paraffined or moisture-
proofed cloth, on which the banding material should then be applied.
The band should be from 4 to 6 inches wide and nearly i/4 inch thick. If
properly applied, these bands will need no attention for several months.

32 University of California — Experiment Station

CONTACT INSECTICIDES

Saturation of the nest with kerosene is very effective against fire ants,
lawn ants, and ants beneath or between paving stones. The kerosene kills
on contact and makes the soil undesirable for nesting. Commercial fly
sprays can also be used effectively to reduce the population of ants but
do not serve as permanent remedies.

Formula 3
Kerosene and Pyrethrum Mixture

Pyrethrum 14 pound

Kerosene 1 gallon

Mix thoroughly. After allowing to stand for about 12 hours, pour off
the clear liquid. This mixture is useful against timber ants, which dis-
appear when it is injected into the timbers occupied by them.

Formula 4
Nicotine Sulfate (Black Leaf 40)

Nicotine sulfate (commercial) 1 part

Water 800 parts

Nicotine sulfate kills the aphids on which ants feed and causes the
ants to leave. Use this mixture as a spray.

Formula 5

Soap Wash

Common laundry soap % to 1 pound

Water 1 gallon

Use this wash, after soap has dissolved, on lawns that have become in-
fested with ants.

FUMIGANTS

Carbon Disulfide. — With a sharply pointed stick, make several holes
slightly larger than a lead pencil and about 6 to 8 inches deep in the
nest. The depth and number of the holes will vary with the nature of
the nest. Into each pour about 1 tablespoonful of carbon disulfide, which
may be applied with a machine oilcan. Cover the whole area treated with
a metal tub, a wet canvas, a wet blanket, or a wet burlap bag. Cc.rbon
disulfide is a highly volatile inflammable liquid and mixtures of its
vapor with air are highly explosive.

Cyanide Powder. — Calcium cyanide is generally sold in the form of
a powder for pest control.

A convenient method of placing the powder in the ant nest is to use a
tin funnel with a long spout and a sharpened stick. After the hole is

CiR. 342] Ants and Their Control 33

made with the stick inside the funnel, the stick is withdrawn, and the
powder poured into the hole through the funnel. The entire nest should
then be covered with soil and the latter packed down firmly.

The amount of cyanide and the depth to which it is to be placed de-
pend upon the size and construction of the nest. From l^ to I/2 pound
of Cyanogas may be necessary for the larger nests of the harvester ants.
Cyanide, a most powerful poison, must he handled carefully. It must
he kept away from the mouth, from sores, and even from the wet shin.
The fumes or dust should not he inhaled. Gas masks should he worn for
greatest safety.

Formula 6
Ethylene Bichloride and Carbon Tetrachloride Mixture

Ethylene dichloride 3 parts (by volume)

Carbon tetrachloride 1 part (by volume)

A fumigant liquid composed of the above mixture is much safer than
carbon disulfide. This combination is not inflammable, explosive, or dan-
gerous to handle. Ethylene dichloride used alone is inflammable and
should be handled with due care.

Formula 7
Pyrethrum and Soap Solution

Contentrated pyrethrum extract 1 part

(With ordinary household pyrethrum insecticides use 2 parts)

Soapy water 1,000 parts

To kill colonies among growing plants, use formula 7 to wet the in-
terior of the nests thoroughly. Scrape away the top of the nest to make a
saucerlike depression and pour the liquid into this so that it will pene-
trate to the bottom of the nest. ■

STOMACH POISONS

Formula 8
Sodium Arsenite (U. S. Government Formula)

Sugar granulated 1 pound

Tartaric acid (crystallized) 10.3 grains

Benzoate of soda 14.6 grains

Water 1 pint

Sodium arsenite 26 grains

Honey 2% ounces

Specific directions for preparing this sirup are as follows :

Warm 1 pint of water in a clean vessel over a low fire, ^^en it is

tepid, add the tartaric acid, then benzoate of soda, and then the sugar,

slowly, and stir constantly to prevent burning. Measure the depth of

the liquid with a stick. Slowly bring it to a boil, and allow it to simmer

34 University of California — Experiment Station

for 30 to 40 minutes. Remove from the stove, and add water to original
depth on the measuring stick to make up for evaporation. Stir in the 2i/3
ounces of honey before the mixture cools. Then add 26 grains of sodium
arsenite w^hich has been dissolved in 1.8 fluid ounces of hot water and
partially cooled before pouring into the sirup. Stir thoroughly. Apply
in containers as previously described.

Formula 9
The California Argentine Ant Sirup

Honey (any aromatic kind) 18% ounces

Tartaric acid (crystallized) 10.3 grains

Benzoate of soda 14.6 grains

Water 1 pint

Sodium arsenite 26 grains

By substituting an equal amount of an aromatic honey for the sugar
in formula 8, a poison sirup is obtained that will give as good or better
results in the control of the Argentine and other sweet-loving ants. A
dark off-grade honey will serve as well as a table variety of honey, and
has the advantage of being cheaper.

Since honey contains primarily invert sugars, the tartaric acid can
also be omitted. The mixture need be boiled for only a few minutes to
insure a uniform solution and to destroy yeasts and mold-forming
organisms. The modified formula will thus contain 18% ounces of honey
dissolved in 1 pint of water, 14.6 grains of benzoate of soda (as a pre-
servative) , and 26 grains of sodium arsenite dissolved in 1.8 fluid ounces
of hot water. The sodium arsenite solution should be mixed thoroughly
with the honey solution. The material should be stored for use in stop-
pered bottles properly labeled to indicate its poisonous nature. It is
distributed in ant tins having openings too small for bees to enter.

Formula 10
Grease Baits

Sodium arsenite 10 grains

Grease 1^/^ pints

Warm the grease and mix thoroughly with the sodium arsenite.

Pieces of bacon into which have been rubbed small quantities of
sodium arsenite are also effective for fat- or grease-loving ants. The
poisoned bacon should be cut in small pieces and distributed in ant tins
as described for poisoned sirup mixtures.

• Formula 11

Sodium Fluoride and Pyrethrum

Sodium fluoride 6 ounces

Pyrethrum (fresh) 2 ounces

Cornstarch 2 ounces

CiR. 342] Ants and Their Control 35

When dusted freely, this mixture has very effectively controlled Mono-
morium destructor on shipboard. It is also effective against the Cali-
fornia velvety tree ant.

Formula 12
Tartar Emetic and Sugar Sirup

Tartar emetic 1 part by weight

Sugar 10 parts by weight

Water 100 parts by Aveight

This should be thoroughly mixed. It is not effective against the Argen-
tine ant. The addition of honey makes it more attractive to ants.

ANTIDOTES AND EMETICS'

Avoid the need of antidotes and emetics by exercising care in properly
labeling poison containers, and by storing them out of reach of children
and away from foodstuffs or medicines, and by using extreme care in
handling the poisons.

GENERAL INSTRUCTIONS

In Case of Poisoning Call a Physician Immediately. Until the physician
arrives follow the directions here given.

When the nature of the poison is unknown, the following is a good
antidote to most poisons, but of little or no value in poisoning by anti-
mony, caustic alkalies, or phosphorus :

Equal parts of magnesia, charcoal (wood), and hydrated oxide of
iron, mixed and freely given in water (2 ounces of each to 12 ounces of
water). The magnesia is given to neutralize any acid that may be pres-
ent ; the charcoal, to precipitate or absorb any alkaloid ; and the hydrated
oxide of iron, to combine with any arsenical compound. On a similar
basis, the following may be given :

Magnesia, 1 tablespoonful ; tannic acid, 1 tablespoonf ul ; charcoal, 2
tablespoonfuls. Mix and give 1 teaspoonful, stirred in water, every 5 to
15 minutes. Evacuate the stomach soon after using this antidote.

The emetics, demulcent drinks, stimulants, and sedatives mentioned
in connection with the specific antidotes are best made as follows :

Emetics. — Mix from two to four teaspoonfuls of mustard in a cupful
of warm water and stir to a thick cream, or give from 15 to 30 grains of

^ The antidotes and emetics given herein have for the most part been taken from :
California State Board of Pharmacy. Ofl&cial antidotes. 7 p. July 1, 1935. Bound in:
Pharmacy law, poison law, veronal law, vendor law, and inspection record. California
State Board of Pharmacy. July 1, 1935.

Some have also been taken from: Brundage, Albert. Manual of toxicology. 15th ed.
444 p. D. Appleton and Co., New York City, 1929.

36 University of California — Experiment Station

powdered ipecac in water; repeat every 10 to 15 minutes; or give from
5 to 10 grains of sulfate of zinc in water and repeat until free vomiting
is produced. (Do not give zinc sulfate if salt and water have been given
previously. )

Demulcent Drinks. — Flaxseed or slippery elm tea, barley water, thin
starch, water, milk, white of eggs mixed with water, or thin flour paste ;
give any of these very freely.

Stimiclants. — Put from 10 to 20 drops of aqua ammonia in half a glass
of water ; or put from one-half to one teaspoonful of aromatic spirits of
ammonia in one-half glass of water; give for one dose and repeat as
needed.

Sedatives. — Give from 1 to 2 tablespoonfuls of paregoric in one-half
glass of water ; or give 30 grains of potassium bromide in water for a
dose and repeat as required.

SPECIFIC ANTIDOTES

Arsenic and Its Compounds. — Emetic of mustard (p. 35) ; hydrated
oxide of iron and magnesia, a cupful ; follow with olive oil or white of
eggs, mucilaginous drinks; 30 grains potassium bromide in water; if
much pain, give 2 tablespoonfuls paregoric in water.

Carbolic Acid (Phenol). — Dilute alcohol, 4 tablespoonfuls of alcohol
with equal amount of water, followed immediately by an emetic of
mustard; repeat three or four times and give albuminous substances,
milk or white of eggs. Follow with Epsom salts.

Carbon Disulfide and Carbon Tetrachloride. — If vomiting has not
occurred, resort promptly to any method of flushing out the stomach,
or to the use of emetics.

Corrosive Sublimate (Bichloride of Mercury). — Fantaus antidote,
white of eggs, flour or starch mixed with water. Follow with an emetic of
mustard. Afterward give strong tea or coffee; stimulants of diluted
alcohol, or a teaspoonful of aromatic spirits of ammonia in water, and
lastly, demulcent drinks. (Fantaus solution is made as follows : sodium
hypophosphite, 5 grams ; hydrogen peroxide, 25 cc ; distilled water, 50 cc.
This amount is necessary to neutralize one antiseptic tablet of 0.5.)

Cyanide (Hydrocyanic Acid). — For cyanide gas poisoning inhale
strong ammonia fumes intermittently. Keep patient quiet and warm. If
not breathing normally, administer artificial respiration. Give V2 tea-
spoonful aromatic spirits of ammonia in 2 ounces of water by mouth.

CiR. 342] Ants and Their Control 37

For cyanide poison swallowed cause vomiting without delay by put-
ting a finger down the throat. Cause patient to swallow a mixture of 2
fluid ounces each of ferrous sulfate (15 per cent solution) and sodium
carbonate (6 per cent solution). Inhale ammonia fumes and apply arti-
ficial respiration. Keep patient quiet and warm.

Sodium Fluoride. — Give at once large draughts of lime water or weak
calcium chloride solution, stimulants of strong coffee or aromatic spirits
of ammonia; artificial respiration; keep lower extremities and chest
warm ; give digitalis hypodermically.

Nicotine Sulfate (Black Leaf 40). — Drink warm water freely; give
emetic of mustard or empty the stomach with a stomach tube. Give
strong tea or coffee, aromatic spirits of ammonia, 1 teaspoonful in
water. Keep lower extremities and chest warm. Give %o grain strych-
nine hypodermically every hour until four doses are taken.

Pyrethrum. — Cause vomiting and evacuation.

Tartar Emetic (Antimony). — Tannin or tannates (strong tea or in-
fusion of oak bark) emetic of mustard and large draughts of warm
water ; afterward white of eggs or milk.

17wi-7,'37