Red Imported Fire Ant Biology
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The scientific name of the red imported fire ant is
Solenopsis invicta. It was taxonomically identified by Dr. William
Buren in 1972, he chose invicta specifically due to its meaning --
invincible. It was earlier identified as Solenopsis saevissima Forel
var. richteri. However, S. invicta is the name under which much
of the research on this insect pest has been
published. |
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It is placed
in the Solenopsis genus by its 10 segmented antennae with a 2-segmented
club. It also has a stinger, a 2 segmented pedicel, and an unarmed
propodeum.
Solenopsis invicta's common name is the red imported fire ant. Like
other fire ants it derives part of its common name from the intense 'fire'
sensation felt by a person when they are stung by it. Its common name
differentiates it from the black imported fire ant. |
Life Cycle of the Red Imported
Fire Ant
The general biology of RIFA has been
determined, however, there are numerous aspects of its biology that are not
fully understood.
Queen
The queen is the matriarch of the fire ant
colony. Living upwards of 6 years, her sole work in life is production of eggs.
A fully mature queen can produce 1000 eggs/day. The red imported fire ant
species is different from some ant species in that two distinct 'lines' that
have emerged. There are monogyne and polygyne colonies. That is, there are
colonies in which there is only one queen, and others where multiple queens are
able to survive within a colony. Researchers have found that in polygyne
colonies there is a dominant queen to which a majority of workers will be
attracted. Co-existing queens are tolerant of each other, but are competitive on
a reproductive level.
Workers/Foragers Workers
are sterile females whose work within and outside of the colony is mediated by
the needs of the queen and the brood. There are major and minor workers -- they
are differentiated by head capsule width.
A generalized time line for
each stage:
- From Egg to Larvae --- 7-14 days
- From Larvae to Pupae --- 12-15 days -- RIFA
larva have four molts prior to pupation
- From Pupae to adult --- approximately 10
days
- From egg to adult it takes 20-45 days
--- on average -- 30 days
General Behavior/Colony Life
There are several behavioral
characteristics that identify this insect pest. One of the characteristics of
RIFA is the type of mound it constructs.
Unlike native ants, RIFA mounds do not have
one central opening into the colony. An extensive tunneling system is present
within the mound.
The network of tunnels inside the mound can
convey sound to the limits of the colony. Sounds somewhat louder than a whisper
have been measured from disturbed fire ant colonies.
Queen
Although the queen is the matriarch of the colony,
she is not in total control. She is dependent on worker ants to care and feed
her.
Worker/Foragers
The ants which work in a colony have many roles ---
nurse, mound builder, mound defender, and forager. The age of the ant determines
some of its role, and the size also. Young ants (nurse ants) are found with the
brood. As they age they move into the reserve stage where they can be found
repairing tunnels in the mound or aggressively defending the mound against
intruders. The oldest ants are generally the foragers.
Brood (pupae, larvae)
Brood, the non-mobile stage of fire ants, are not
entirely without means of communication or behavior. Although little research
has been conducted on this life stage observations that have been made are quite
insightful. For example, it has been observed that larva will rock back and
forth to draw attention to themselves so that workers will feed it.
Reproductives
An individual colony enters into a reproductive
stage relative to competition and availability of food. Reproduction begins with
nuptial flights. When environmental conditions are good (generally after a
rain), workers will create holes in the mounds surface where male ants leave the
nest and form large masses in the air. The female then leaves the nest and she
flies into this aggregation of males. Male and females mate in the air. Within a
short period of time, the male is dead. After mating the female --- now a queen
-- then begins the process of starting a new colony.
This fact sheet was prepared
by the
California Department of Food and
Agriculture,
with supplemental information provided by the
Texas Agricultural Extension Service.
