July 2013 Articles

Archives by Months

Insect Management - Red Imported Fire Ants - General Biology

Insect Management— Red Imported Fire Ants— General Biology Source: www.aragriculture.org
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 choseinvicta 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.
Photos of various mounds
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
Insect Management—Red Imported Fire Ants
Community Abatement
Community involvement is important for any effective control of the red imported fire ant (RIFA). Several communities throughout the United States have developed abatement programs to minimize the impact of this insect. There are several types of abatement programs which a community can develop. Some communities have area-wide treatment dates in which the homeowner elects to purchase the appropriate pesticide and apply it within a specified period, while other communities involve individuals who apply the pesticides at the appropriate period, and the community pays him/her a fee for services. Providing pesticides at cost to the consumer is another way communities have become involved in fire ant control.
Abatement Programs in Arkansas
Grant County—Hope—Little River County—Sevier County -Texarkana
Arkansas Fire Ant Advisory Board The Arkansas State Legislature passed an bill in 1997 related to development of fire ant abatement districts. The current Act provides a framework for communities to develop fire ant abatements districts Act 590. We plan to run a segment on Fire Ants over the next few months, until we complete the articles from Uof A.