Fire Ants!

• In the 1930’s, 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.

Origin

The Current Port of Mobile, Alabama

South America Stow Away Ants

The RIFA – Solenopsis invicta

http://www.aphis.usda.gov/plant_health/plant_pest_info/fireants/downloads/fireant.pdf

© RWR

Photo credit: Alex Wild - myrmecos.com

10/2/2008

• 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.

Demonstrating Infected Areas Under Quarantine

• Females have a shiny red head with a black back segment.

• Males are totally black• Size: 2.4 6 mm

General Characteristics

• 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.

Behavioral Tendencies

• 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.

RIFA Mounds

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 tunnelExit / Entrance

Lateral foraging tunnel

Deep tunnels to water source

Interconnectedchambers

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

PupaAdult

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).

Cost Estimates

http://www.ars.usda.gov/fireant/impact.htm

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

“Fire Ants ATTACK!”

Fire Ant “Bites”

Fire AntBaits

Chemicals for Fire Ant Control

Biological Control

Predatory flies(Phoridae)

Phorid Fly Selecting a Victim

Fire Ant Decapitated by Phorid Fly

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

© RWR

S. invicta Venom Alkaloids

•Unique among stinging insects

– ~95% alkaloids and ~5% proteins

•Potential for alkaloid toxicity unknown

Venom contains mixture of several forms – isosolenopsins – solenopsins– dehydrosolenopsins)

Synthesis by National Center for Natural Products Research (Ole Miss)

NH

(CH2)nCH3

(2R,6R)-Solenopsin A(2R,6R)-Solenopsin B(2R,6R)-Solenopsin C

n=10n=12n=14

NH

(CH2)nCH3

(2R,6S)-Isosolenopsin A(2R,6R)-Isosolenopsin B(2R,6R)-Isosolenopsin C

n=10n=12n=14

NH

CH

CH

(CH2)7CH3(CH2)n

(2R,6R)-Dehydrosolenopsin B(2R,6R)-Dehydrosolenopsin C

n=3n=5

10/2/2008

Entomology Humor