I. b. Imported Fire Ant
Identification and Biology
Teaching Module for Master
Gardener Training
Identification
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Location – found in
open, sunny areas
Mounds – large, no
activity on surface
Ants – very
aggressive when
disturbed
Stings – Painful,
leave white pustule,
sting more than
once
Medical Importance
Pustules
Bite and Sting
Multiple Times
Stinger and Poison Gland
Types of Adult Fire Ants
Winged
female
Winged male
Workers
UC Statewide IPM Program
Polymorphism in Worker Ants
major
queen
minor
media
Adult fire ant workers have different morphs (polymorphic), i.e.
major, media and minor that vary greatly in body size. Majors are
often used in identification because of their large size. Not all ant
species exhibit polymorphism.
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 (8003000 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
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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