ifficult, even for experts. Identification usually requires 40 or more randomly collected worker ants for study.
Black Imported Fire Ant. The black imported fire ant, Solenopsis richteri, is very similar to the red imported fire ant. Its current distribution is limited to a small area of northern Mississippi and Alabama. It may be displaced from established habitats by the red fire ant. Scientists have long thought that the black and red fire ants were 2 distinct species. Recently it has been discovered that hybrids of these ants produce viable offspring, and some scientists now wonder whether they are simply 2 races of the same species, varying in color and perhaps behavior.
Southern Fire Ant. The southern fire ant, Solenopsis xyloni, is a native species that occurs from North Carolina south to northern Florida, along the Gulf Coast and west to California. In California it occurs in the lower altitudes from Southern California up through Sacramento but is seldom found along the coast in central to northern California. This is probably our most common native species of ant but its distribution is greatly retarded when the Argentine ant is present. However in areas where the Argentine ant is controlled, populations of this species rapidly return.
Colonies may be observed as mounds or more commonly may be constructed under the cover of stones, boards, and other objects or at the base of plants. These ants also nest in wood or the masonry of houses, especially around heat sources such as fireplaces. Nests often consist of loose soil with many craters scattered over 2 to 4 square feet. In dry areas nests may be along streams, arroyos, and other shaded locations where soil moisture is high. Southern fire ants usually swarm in late spring or summer.
The workers are very sensitive to vibrations or jarring. If their nest is stepped on they will rush out and sting the feet and legs of the intruder. Individual reaction to their venom is quite variable depending on allergic reaction. There is a least one case of a human infant death due to mass stinging of this species.
This species is practically omnivorous feeding on a variety of materials including honeydew, meat, seeds, fruit, nuts, cereal and cereal products, grease and butter and dead and living insects. It can be quite detrimental to agriculture foraging for seeds from seed beds, girdling nursery stock, and consuming fruits and vegetables. In addition these ants will remove insulation from wiring and occasionally gnaws on a variety of fabrics.
Fire Ant. The fire ant, Solenopsis geminata, is a native species sometimes called the tropical fire ant. It ranges from South Carolina to Florida and west to Texas. It is very similar to the southern fire ant except its head is much larger and the petiole node is higher and narrower. This species usually nests in mounds constructed around clumps of vegetation, but may also nest under objects or in rotting wood.
Red Imported Fire Ant. The red and black imported fire ants were first reported in the United States in 1929. It is thought that they came to the port in some soil used as ballast in the bottom of a cargo ship. Since this introduction the black fire ant has not spread as rapidly as the red imported species. By 1953 (first official USDA survey) the red imported fire ant had spread to over 100 counties in 10 states. Today it is prevalent throughout the southeastern US and has moved into Texas, New Mexico. Arizona and California.
Natural movement of fire ants is limited to mating flight or by rafting during period of flooding. However, the rapid movement of these species across the South and westward is mainly associated with human activity. In this case the initial spread of these ants in the southeastern US was thought to be due to movement of sod and potted ornamental plants. This inadvertent movement of S. invicta and S. richteri was noted by the U.S. Department of Agriculture in 1953 when a direct link was established between commercial plant nurseries and the spread of imported fire ants. In response to mounting public pressu