Nevada County Picayune and Gurdon Times Newspaper Archive

Fire Ants Will Return With Warm Weather; Hard To Kill

Fire ants may not be at the top of the ground now, but most residents in south Arkansas know they are around. However, with the warm weather thus far this winter, some are active.

The imported fire ant, a native of South America, probably arrived in the United States by two separate introductions. The black imported fire ant, Solenopsis richteri, arrived in Mobile, Ala., in 1918. The red imported fire ant, Solenopsis invicta, was introduced into Mobile in the 1930's.

Both species likely came to the U.S. in soil used as ballast on South American cargo ships.

The red imported fire ant spread from Mobile to other areas across the south. The black imported fire

ant is now only found in northern parts of Mississippi and Alabama and southern Tennessee.

Spread of the fire ant is due not only to natural mating flights, but also to the movement of infested plants, sod, and soil.

In 1958, the Federal Fire Ant Quarantine was enacted to try to prevent the spread of fire ants from quarantined areas, but the ant continues to spread at the rate of five to 12 miles per year. Eventually fire ants are expected to infest almost one-fourth of the United States, including the western seaboard, where temperature and moisture are adequate.

Northward spread of fire ants has been limited by cold weather, but colonies can survive in northern areas by building their nests under roadways, against concrete slabs and in external walls of heated buildings.

Distinguishing between ant species is sometimes difficult and some species of fire ants are native to the U.S.

One method of identifying imported fire ants is by their mounds. Imported fire ant mounds are usually built in open sunny areas, sometimes supported by a wall, post or shrub.

The mound has no external openings; underground tunnels radiating from the mound allow ants to come and go in search of food. The number of ants determines the size and growth of each colony. Beginning colonies are generally a few inches across, compared to older colonies which may be in excess of two feet or more in height and diameter.

The mound is a series of interlocking tunnels and chambers which may reach more than five feet below the surface. Location of ants within the mound is dependent on weather conditions, water level and other factors.

Fire ants are best known for their aggressive behavior. If their mound is disturbed, they defend it by swarming out and over the mound, even running up grass blades and sticks.

Fire ant colonies are established by newly mated queens following a mating flight. If the queen lands on a suitable area, she removes her wings and excavates a small chamber in the soil. Within 24 hours, the queen begins laying eggs, which she will care for. Later eggs are cared for entirely by the new worker ants.

All tasks of maintaining the colony are carried out by the sterile

female workers, except egg production which is now the queen's only function.

If fire ant queens survive the first few months after mating, they may live approximately six years. Mortality of fire ant queens during the first few months is often as high as 99%. Workers have a much shorter life span, usually several months.

Workers of many different sizes make up the fire ant colony. The largest workers are called majors; the medium-sized workers are called medias; and the smallest workers are minors. However, the age of the worker ant, not her size, determines what tasks she will eventually perform.

A mature colony will contain 100,000 to 500,000 workers and several hundred "reproductives."

Reproductives are winged males and females that accumulate in the colony until weather conditions are

favorable for mating flights. After mating, the new queen falls to the ground to begin a new colony, the male falls to the ground and dies.

Eggs of the fire ant hatch in seven to10 days into grub-like larvae. Larvae are totally dependent on workers for their care.

During the following six to 12 days, larvae will molt four times. After the fourth molt larvae become pupae. Adults emerge in nine to 16 days.

Newly emerged adults first act as nurses, feeding and grooming the queen and the eggs, larvae and pupae, called brood. As they grow older, they become reserves that continue to care for the brood, but also help to build and defend the mound and to help retrieve food.

The oldest ants in the colony are the foragers. They are responsible for locating food to feed the colony. When a food source is found, the foragers lay a chemical trail back to the mound where they recruit the reserves to help transport it back to the colony. Use of this recruitment system allows fire ants to quickly and efficiently provide food for their colony, out-competing all other ants.

Fire ant colonies need large amounts of carbohydrates, proteins and fats to keep them going. They

get most of their carbohydrates from eating plant sap and most of their proteins and fats from eating dead animals or those they kill. Fire ants are especially fond of insects.

All food for the fire ant colony must be in liquid form, the adult ants cannot digest solid food. Ants may extract liquids from the food source immediately or they may bring the food particle back to the mound.

Particles are given to the largest larvae, the only stage of the fire ant life cycle that can digest solid food. These larvae secrete enzymes to digest the food and the resulting liquid is used to feed the workers and queen. This liquid food is distributed throughout the colony by trophallaxis (the exchange of liquid food).

The queen controls colony growth and activity by the secretion of chemicals that are passed from worker to worker when they encounter each other, through trophallaxis, and also by the production of replacement workers and reproductives.

Nurses shield the queen from danger by first consuming foods before they are fed to her and by quickly carrying her away if the mound is disturbed.

The colony can endure as long as the queen and a few workers survive. This guarding of the queen makes eliminating a fire ant colony very difficult.

Fire ant colonies may include one or more queens.

Single queen colonies are very territorial toward other fire ants. Newly mated queens landing in the territory of a single queen colony are attacked and killed.

Colony life is different in multiple queen colonies. Workers in these colonies are less aggressive toward workers from other mounds, therefore mounds are closer together, making areas more heavily infested. In multiple queen sites, newly mated queens are often accepted into the colony instead of being killed. Multiple queen colonies may contain a few queens or up to several hundred. Control of these colonies is challenging, because as long as one queen survives the colony can continue.

The aggressive behavior of fire ants and the ability of each worker to sting repeatedly threatens both man and animal.

The sting injects a venom that causes an extreme burning sensation. Pustules form which can become infected if scratched.

Allergic reactions of people sensitive to the venom include dizziness, swelling, shock and in extreme cases unconsciousness and

death. People exhibiting such symptoms should see a physician.

Young animals and birds that are unable to escape can also be threatened.

A population of native ants is one of the few factors that can slow the invasion of fire ants. Newly mated fire ant queens are susceptible to being killed by native ants before they can burrow into the ground. It is therefore important to consider the preservation of native ant species when applying fire ant control measures.

Eradication of imported fire ants is not possible using present day pesticides, because of: 1) the large area of infestation, 2) the relatively small area that can be treated with pesticides, 3) short residual activity of current pesticides, and 4) the rapid re-colonization rate of treated areas.

By using integrated pest management strategies, a reduction in the effects of the fire ant can be accomplished without eliminating the ants themselves.