Insect Management
Red Imported Fire Ants
General Biology
Systematics •
Life Cycle
• Queen •
Workers/Foragers
• Brood (pupae, larvae)
• Reproductives •
Stages • General Behavior/Colony Life •
Mound Photos •
Glossary
Systematics
Entomologists have been classifying insects for several hundred years and a
classification system has developed.
Kingdom - Animalia
Phylum - Arthropoda
Class - Insecta
Order - Hymenoptera
Family - Formicidae
Genus - Solenopis
Species - invicta
(a common acronym - KPCOFGS - Kings Play Chess On Fine Grains of Sand)
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.
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
Although the queen is the matriarch of the fire ant colony, she is not in total
control. She is dependent on worker ants to care for and feed her.
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.
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.
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.
Glossary
Monogyne - single queen colonies
Polygyne - multiple queen colonies
Propodeum - the first abdominal segment fused with
the thoracic segments (syn. epinotum), i.e. appears to be a segment of the
thorax, but it is the first segment of abdomen
Species - a group of individuals or populations in
nature that are capable of producing offspring, and which are reproductively
isolated
Systematics - the study of the diversity of organisms and of the
relationships between them
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