In the 1930s, the red imported fire ant was introduced to the United States at the port of Mobile, Alabama. Originating in South America, it is generally thought that they arrived through soil used as ballast in cargo ships. The Current Port of Mobile, Alabama South America Stow Away Ants
The Animal and Plant Health Inspection Service (APHIS) hopes to inhibit further infestation by regulating the transport of certain items identified in the Federal Quarantine. Imported fire ants currently infest more than 320,000,000 acres across thirteen states and one territory (Puerto Rico). They are considered a pest because of their painful stings, aggressive behavior and affect on numerous agricultural products.
Females have a shiny red head with a black back segment. Males are totally black Size: 2.4 6 mm A mature nest consists of one- quarter million workers. The sole purpose of a male ant is to mate; after which, they die. Sterile female workers and a fertile queen ant are the primary occupants of a nest.
Omnivorous The colony will survive as long as the queen and a few worker ants survive, making them basically impossible to eradicate. The species' Latin name, invicta, means "invincible, which is extremely appropriate considering our incapability to eradicate them. Red imported fire ants are the most aggressive of the imported ants, tending to swarm when disturbed.
They prefer to occupy areas where the temperature mean is 15°C or higher. The mounds are large, cone- shaped domes with hard, weather-resistant crusts. The average size for a mature mound is 10 inches to 24 inches in diameter and 6 inches to 18 inches tall. In heavy clay soil, the mounds may be much larger, sometimes reaching 3 feet in height. Such mounds may have galleries extending as far as 6 feet underground.
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. Reproduction
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
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. eggs Colony Formation
A queen can live 5-7 years and lay up to her own weight in eggs per day (800-3000 eggs). eggs Colony Formation
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 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. Mound Development
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.
The fire ant has 4 life stages Eggs Pupa Adult Larvae
Larvae molt four times over a 12-15 day period. Larval Stages
Fourth instars are the only stage that can feed on solid food (black arrow points to food particle).
Fire ants eat a variety of foods and are excellent foragers. Reagan, LSU AgCenter Food Sources
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.
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 Single Queen Colony
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 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
Economic Cost Of Fire Ants? Estimated total between 1957 and 1984: – $172 million Stings: – 1500 cases of severe allergic reactions/year – 2-5 deaths per year – $2.84 million per year to treat sting victims Crops: – $125 million/year to soybean growers alone – Total estimated economic impact annually: $6 billion C. F. Lard et al., An Economic Impact of Imported Fire Ants in the UnitedStates of America (Texas A&M University, College Station, TX, 2006).
Problems with RIFA Cause numerous environmental and medical problems Destruction to crops, damage to farm equipment, demise of newborn livestock Medical problems include large local reactions, secondary infections from the sting, anaphylactic reactions, neurological manifestations, and even death
Problems Created By Fire Ants Public health problems Agricultural problems Wildlife and the environment Miscellaneous bizarre effects
Attacking en masse, the ants respond to pheromones that are released by the first ant to attack. A fire ant typically bites with its mandibles, then swivels its abdomen and stings repeatedly in an arc about the bite site. When used against prey, it can kill or paralyze. When injected into humans, the toxic alkaloids produce an immediate burning sensation at the entry site. Their stings develop into sterile pustules and then rupture
Sting Burning pain, both bite and sting Attaches itself with its mandibles Arches at the peduncle and inserts the stinger – 0.007 to 0.11 µl of venom is injected – Skin Responses
Venom Young workers use venom during brood care as an antiseptic Older workers use it to capture victims Defense against intruders 95% water-insoluble 2,6-disubstituted piperidine alkaloids Alkaloid components are classified as either solenopsins, isosolenopsins, or dehydrosolenopsins
Venom Classification depends on the enantiomeric configuration and alkyl or alkenyl carbon chain Alkyl chains have either 11, 13, or 15 carbons Composition of alkaloids may be different depending on the size and age of the worker or in a particular nest
Venom Contains 5% soluble proteins Proteins are the active allergens 5% aqueous portion contains four allergenic protein components: – Sol i 1 (37 kD) – Sol i 2 (13.2 kD) – Sol i 3 (24 kD) – Sol i 4 (13.3 kD)
Venom Alkaloids Alters normal physiologic function in rats Inhibit Na + -K + -ATPase pump (mammalian muscle cell) Induce platelet aggregation Hemolytic activity