Fire Ants!
• In the 1930’s, the red imported fire ant
was introduced to the United States at
the port of Mobile, Alabama.
• Originating in South America, it is
generally thought that they arrived
through soil used as ballast in cargo ships.
The Current Port of Mobile, Alabama
South America
Stow Away Ants
The RIFA – Solenopsis invicta
Photo credit: Alex Wild - myrmecos.com
http://www.aphis.usda.gov/plant_health/plant_pest_info/fireants/downloads/
fireant.pdf
© RWR
10/2/2008
• Imported fire ants currently infest more than
320,000,000 acres across thirteen states and
one territory (Puerto Rico).
• They are considered a pest because of their
painful stings, aggressive behavior and affect
on numerous agricultural products.
• The Animal and Plant
Health Inspection Service
(APHIS) hopes to inhibit
further infestation by
regulating the transport of
certain items identified in
the Federal Quarantine.
• Females have a shiny red head with a black
back segment.
• Males are totally black
• Size: 2.4 6 mm
• Sterile female workers and a fertile queen
ant are the primary occupants of a nest.
• A mature nest consists of onequarter million workers.
• The sole purpose of a male ant
is to mate; after which, they
die.
• Omnivorous
• The colony will survive as long
as the queen and a few worker
ants
survive, making them
basically
impossible to eradicate.
• The species' Latin name, invicta, means "invincible“,
which is extremely appropriate considering our
incapability to eradicate them.
• Red imported fire ants are the most aggressive of the
imported ants, tending to swarm when disturbed.
• They prefer to occupy areas
where the temperature mean is
15°C or higher.
• The mounds are large, coneshaped domes with hard,
weather-resistant crusts.
• The average size for a mature
mound is 10 inches to 24 inches
in diameter and 6 inches to 18
inches tall. In heavy clay soil, the
mounds may be much larger,
sometimes reaching 3 feet in
height.
• Such mounds may have
galleries extending as far as 6
feet underground.
RIFA Mounds
Reproduction
 Mating flights on
sunny days 1-2
days after a rain
when temperatures
are above 75ºF
 Flights usually
occur in spring and
fall but can occur at
any time of year
Reproduction
 Mating takes place 300 to 800
feet above the ground.
 After mating, female seeks moist
or reflective surfaces on which to
land; male dies.
 Female vulnerable to predators
during and just after mating flight,
especially other fire ants.
Colony Formation
 New colonies
are founded by
newly mated
females (queens).
 Once a queen
lands, she
removes her
wings, burrows
into the soil and
begins to lay eggs.
Colony Formation
eggs
 First batch of
eggs grows up to
be worker ants.
 Worker ants are
all sterile females
capable of stinging.
 Workers begin
foraging and
constructing
mound.
Colony Formation
eggs
A queen can
live 5-7 years
and lay up to
her own
weight in
eggs per day
(800-3000
eggs).
Development
Worker immature and mature stages
 Large workers live about 90-150 days as adults
 Small workers live about 60-90 days as adults
 Regardless of size, they change jobs as they age
 nurse
 guard/excavator
 forager
Mound Development
 Mounds often
are not clearly
visible within first
few months.
 A small mound
with several
thousand ants
may be visible
within six months.
Mound Development
 Fire ant mounds can be
recognized by their dome or
cone-shape.
 Mounds can be quite large
(sometimes 60 cm tall and
60 cm wide).
 Mounds usually found in
open areas.
 Unlike the nests of most
other ants, fire ant mounds
have no openings and little
visible activity on the
mound surface, unless
disturbed.
Lateral foraging
tunnel
Exit / Entrance
Lateral foraging
tunnel
Deep tunnels to water source
Interconnected
chambers
If the mound is disturbed, the workers rush to save the queen
and the immature ants.
Workers move the
immature fire ants
and the queen
around the nest,
for near constant
temperature and
humidity, often
more than once
per day.
Eggs
The fire ant has 4
life stages
Pupa
Larvae
Adult
Larval Stages
Larvae molt
four times
over a 12-15
day period.
Fourth instars
are the only
stage that can
feed on solid
food (black
arrow points to
food particle).
Food Sources
Fire ants eat a
variety of foods
Reagan, LSU AgCenter
and are
excellent foragers.
Trophallaxis
 Foraging ants bring the food back to the nest.
 The ants pass the food to one another by
regurgitating it from their crops as liquid until
food is distributed to all members of the colony,
including the queen (trophallaxis).
 Adults cannot digest solid food.
Single Queen Colony
15-80 mounds per acre, 7
million ants per acre
 One queen per colony
 Worker ants are
territorial
 The majority of fire ant
colonies are of the single
queen type
Multiple Queen Colony
 200-800 mounds per
acre, 14 million ants per
acre
 More than one queen
in each colony
 Colonies reproduce by
budding
 Worker ants are not
territorial
 Typical form in Texas
Reproduction Type
• Single queen (monogyne)
– territorial and aggressive
– limited life to colony
• Multiple queens (polygyne)
– non-territorial and not aggressive toward
each other
– will adopt new queens
– long-lived colonies
Economic Cost Of Fire Ants?
• Estimated total between 1957 and 1984:
– $172 million
• Stings:
– 1500 cases of severe allergic reactions/year
– 2-5 deaths per year
– $2.84 million per year to treat sting victims
• Crops:
– $125 million/year to soybean growers alone
– Total estimated economic impact annually: $6 billion
C. F. Lard et al., An Economic Impact of Imported Fire Ants in the
UnitedStates of America (Texas A&M University, College Station,
TX, 2006).
Cost Estimates
http://www.ars.usda.gov/fireant/impact.htm
Problems with RIFA
• Cause numerous environmental and medical
problems
• Destruction to crops, damage to farm
equipment, demise of newborn livestock
• Medical problems include large local
reactions, secondary infections from the sting,
anaphylactic reactions, neurological
manifestations, and even death
Problems Created By Fire Ants
• Public health
problems
• Agricultural problems
• Wildlife and the
environment
• Miscellaneous bizarre
effects
• Attacking en masse, the ants
respond to pheromones that are
released by the first ant to attack.
• A fire ant typically bites with its
mandibles, then swivels its
abdomen and stings repeatedly in
an arc about the bite site.
• When used against prey, it can kill
or paralyze. When injected into
humans, the toxic alkaloids
produce an immediate burning
sensation at the entry site.
• Their stings develop into sterile
pustules and then rupture
Fire Ant “Bites”
Fire Ant
Baits
Chemicals for Fire Ant Control
Biological Control
Predatory flies
(Phoridae)
Phorid Fly Selecting a Victim
Fire Ant Decapitated by Phorid Fly
Sting
• Burning pain, both bite and sting
• Attaches itself with its mandibles
• Arches at the peduncle and inserts the stinger
– 0.007 to 0.11 µl of venom is injected
– Skin Responses
Venom
• Young workers use venom during brood care as an
antiseptic
• Older workers use it to capture victims
• Defense against intruders
• 95% water-insoluble 2,6-disubstituted piperidine
alkaloids
• Alkaloid components are classified as either
solenopsins, isosolenopsins, or dehydrosolenopsins
Venom
• Classification depends on the enantiomeric
configuration and alkyl or alkenyl carbon chain
• Alkyl chains have either 11, 13, or 15 carbons
• Composition of alkaloids may be different
depending on the size and age of the worker
or in a particular nest
Venom
• Contains 5% soluble proteins
• Proteins are the active allergens
• 5% aqueous portion contains four allergenic
protein components:
– Sol i 1 (37 kD)
– Sol i 2 (13.2 kD)
– Sol i 3 (24 kD)
– Sol i 4 (13.3 kD)
Venom Alkaloids
• Alters normal physiologic function in rats
• Inhibit Na+-K+-ATPase pump (mammalian
muscle cell)
• Induce platelet aggregation
• Hemolytic activity
S. invicta Venom
Alkaloids
N
H
(2R,6R)-Solenopsin A n=10
(2R,6R)-Solenopsin B n=12
(2R,6R)-Solenopsin C n=14
•Unique among
stinging insects
– ~95% alkaloids
and ~5% proteins
•Potential for
alkaloid toxicity
unknown
N
H
(CH2)nCH3
(2R,6S)-Isosolenopsin A n=10
(2R,6R)-Isosolenopsin B n=12
(2R,6R)-Isosolenopsin C n=14
H
N
H
(CH2)n
(CH2)nCH3
H
C
C
(CH2)7CH3
(2R,6R)-Dehydrosolenopsin B n=3
(2R,6R)-Dehydrosolenopsin C n=5
Venom contains mixture of several forms
–
–
–
isosolenopsins
solenopsins
dehydrosolenopsins)
Synthesis by National Center for Natural
Products Research (Ole Miss)
© RWR
10/2/2008