II. a. Imported Fire Ant
Introduction and Biology
Teaching Module for Advanced
Master Gardener Training
Where are imported fire ants from?
Where are they found in the US?
Need new map
History of Imported Fire Ants
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1918: estimated introductions occurred of black
imported fire ant (Solenopsis richteri)
First introduced in Mobile, Alabama
Red imported fire ant (S. invicta) followed in
the early 1930’s
The two species have hybridized
Imported fire ants currently infest 330 million
acres in the U.S.
No natural enemies native to U.S.
History
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IFA are the most
destructive and costly
ants in the U.S.
IFA thrive in disturbed
habitats, natural or
man-made disturbances
IFA continue to expand
in the U.S. and their
final range has yet to be
reached
Identification
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Habitat – 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
Pustules
Bite and Sting
Sting 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, which greatly vary in body size.
Majors are often used in identification because of their large
size. Not all ant species exhibit polymorphism.
Fire Ant Anatomy – Major Body Parts
AL=
AN=
CE=
G=
H=
M=
MT=
P=
PP=
PR=
PT=
S=
T=
alitrunk
antenna
H
compound eye
gaster
head
mandible
AN
mesothorax
petiole
post-petiole
propodeum
prothorax
sting
teeth (mandibular)
AL
PR
PT MT
PP
CE
M
T
Solenopsis
G
S
P
Solenopsis invicta Buren
Imported Fire Ant Anatomy
USDA
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Reddish to brown in
color
Large eyes
Workers are polymorphic
(1/6 – 1/5 in. long)
Waist with 2 nodes
No spine on propodeum
10 antennal segments
2-segmented antennal
club
Brown gaster with
stinger
Extremely aggressive
Photos
by
AntWeb
Comparing RIFA to a Carpenter Ant
Red Imported Fire Ant
April Noble, Antweb.org
Common Black Carpenter Ant
Alex Wild 2003
Relative
Size of Ant
Workers of
Various
Species
Texas Imported Fire Ant Research &
Management Plan
Mating and Dispersal
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Mating flights occur
on sunny days within
24 hours of rain,
when temperatures
are above 75ºF.
Flights usually occur
in spring and fall, but
may occur after any
rainfall.
Mating and
Dispersal
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Mating takes place 300 to
800 feet above the ground.
After mating, females seek
moist or reflective surfaces
on which to land; male dies.
Female is vulnerable to
predators during and just
after mating flight,
especially to other fire ants.
Colony Development
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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 Development
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The first batch of eggs grow up to be worker ants
Takes 20 – 45 days for adult maturity
Worker ants are all sterile females capable of stinging
Workers begin foraging and constructing the mound
A Queen’s Life
EGG
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After the first batch of workers is grown, the queen will
always be tended by her workers.
The queen can live 5-7 years and can lay eggs equal to
her own body weight each day.
Mound Development
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Mounds often not
visible the first few
months
Within six months a
small mound
becomes visible
May have 100,000
ants present
Mound Development
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Mature mounds may
be quite large
- Distinctive trait
Mature colonies may
contain 200,000 to
400,000 worker ants
- Polymorphic
colony population
Mound Structure
Lateral foraging
tunnel
Exit / Entrance
Lateral foraging
tunnel
Deep tunnels to water source
Interconnected
Chambers
If the mound is disturbed…
Workers rush to save the queen and the
immature ants
Colony Life
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Workers move the
young fire ants and the
queen around the nest
Often move more than
once per day
Maintains near constant
temperature and
humidity
Fire Ant Life Stages
Egg
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Pupa
Larvae
Complete
metamorphosis
4 life stages
Adult
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Eggs found in brood chamber of a mound
Eggs usually take 7-10 days to hatch
Larval Instars
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Larvae molt four
times over 12-15 day
period
First three instars fed
regurgitated liquid
food
Black arrows
point to a
piece of
solid food in
the food
basket
below the
mouth
Fourth instars are the only stage that can feed on solid food
Fire Ant Diet
Fire ants eat a
variety of foods
Pollet, LSU AgCenter
and are
excellent foragers
What do fire ants eat?
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Mostly other insects
(predators)
Tend aphids and scale
insects for honeydew
Plants and seeds that
produce oils
Fire ant workers DO
NOT eat solid food
Feed by trophallaxis
Trophallaxis
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Foraging ants bring food
back to the nest.
Ants pass the food one to
the other by regurgitating
it from their crops.
Adults pass liquid food
around.
Adults cannot digest solid
food.
Food is distributed to all
members of the colony,
including the queen.
Fire Ant Development
Worker immature and mature stages
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Large workers live about 90-180+ days as adults
Medium workers live about 60-90 days as adults
Small workers live about 30-60 days as adults
Regardless of size, they change jobs as they age
- nurse
- guard/excavator
- forager
Development of Castes
Worker immature and mature stages
Egg
Queen
Reproductive immature and mature stages
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Pattern of development similar for worker and reproductive
stages
Males develop from unfertilized eggs
Female reproductives get special food and hormones
Two Types of Colonies
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Single queen (monogyne)
- territorial and aggressive
- limited life span of the colony
Multiple queens (polygyne)
- not territorial or aggressive toward each other
- will adopt new queens
- long-lived colonies
Monogyne Queen Colony
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15-80 mounds per acre
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Up to 7 million ants/acre
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One queen per colony
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Worker ants are territorial
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Found in all southeastern
states in the U.S.
Polygyne Queen Colony
 200-800 mounds per acre
 Up to 14 million ants per acre
 More than one queen in each
colony
 Colonies reproduce by
budding
 Worker ants are not territorial
 Predominant form in Texas
For More Information:
http://www.extension.org/fire+ants
Publications, slide sets, streaming video, posters, and more…
Acknowledgments
Thanks to the Texas Imported Fire Ant Research &
Management Plan, Texas A&M University System, for the
use of many of the images seen in this presentation.
Portions of this presentation were made possible by a grant
from the Southern Region Sustainable Agriculture Research
and Education Professional Development Program.
Authors:
- Kerry Smith – Alabama Cooperative Extension System
- Molly Keck – Texas AgriLife Extension Service
- Bart Drees – Texas AgriLife Extension Service
- David Williams – University of Florida
- Ken and Rufina Ward, Alabama A&M University
Acknowledgments
Reviewers:
- Dale Pollet – Louisiana State University AgCenter
- Karen Vail, University of Tennessee
- Chazz Hesselein, Alabama Cooperative Extension System
- Kathy Flanders, Alabama Cooperative Extension System
Editor, Technical Facilitator:
- Neal Lee