Fire ants are stinging ants of the genus Solenopsis, of which there are over 280 species and subspecies worldwide. Most species are unobtrusive, and rarely come into contact with humans, and of the few that do, most do not attain the status of serious pests, as they are kept in check by parasites and predators, as well as competition with other ants. However, at least one species, Solenopsis invicta, commonly known as the Red imported fire ant (RIFA), has been moved around the world from its native range in South America and, in the absence of its predators and parasites, has become a major pest nearly everywhere it has been introduced, as is common for invasive species. This species was accidentally introduced into the United States via Brazilian cargo entering the port of Mobile, Alabama, in the 1930s. The ants have since spread from coastal areas of Alabama and now infest large parts of the U.S. South, creating a nuisance to farmers and homeowners alike from California to Maryland. Since 2001, this species has been spread to eastern Australia, the Philippines, Taiwan, and China.
A typical Solenopsis colony produces large mounds in open areas, and feeds primarily on young plants and seeds. Solenopsis often attacks small animals and can kill them. Unlike many other ants, which bite and then spray formic acid on the wound, fire ants only bite to get a grip and then sting (from the abdomen) and inject a toxic alkaloid venom. For humans this is a painful sting - hence the name fire ant - and the after effects of the sting can be deadly to sensitive individuals. The worker ants are blackish to reddish and vary from 3-6 mm in length. The diagnostic feature for the genus Solenopsis is the possession of a single median seta on the anterior clypeal margin.
Carpenter ants are large, black ants (1/4" - 1") indigenous to large parts of the world. They prefer dead, damp wood in which to build nests. Sometimes carpenter ants will hollow out sections of trees. The Carpenter Ant is one of the more destructive pests found in homes. Colonies that remain undetected and untreated can grow to as large as 8,000 workers and can cause severe structural damage. Contrary to popular belief, Carpenter Ants do not actually eat the wood. They remove it, leaving smooth holes and halls through the wood. Small inexplicable piles of shavings similar to pencil shavings below windows or below openings in baseboards are one possible sign of an infestation. Locating and eliminating the actual colony is the only way to effectively treat this problem.
All ants in this genus possess an obligate bacterial endosymbiont called Blochmannia. This bacterium has a small genome, and retains genes to biosynthesize essential amino acids and other nutrients. This suggests the bacterium plays a role in ant nutrition. Many Camponotus species are also infected with Wolbachia, another endosymbiont that is widespread across insect groups.