Fire ant
Fire ants are several species of ants in the genus Solenopsis. They are, however, only a minority in the genus, which includes over 200 species of Solenopsis worldwide. Solenopsis are stinging ants, and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many species also are called red ants because of their light brown color, though species of ants in many other genera are so named for similar reasons. Examples include Myrmica rubra and Pogonomyrmex barbatus.[2]
None of these names apply in all countries nor to all species of Solenopsis, nor only to Solenopsis species; for example the colloquial names for several species of weaver ants in the genus Oecophylla in Southeast Asia include “fire ants” because of their red color and painful sting; the two genera, however, are not closely related. Also, Wasmannia auropunctata is commonly called the “little fire ant”.[3]
The bodies of mature fire ants, like the bodies of all typical mature insects, are divided into three sections: the head, the thorax, and the abdomen, with three pairs of legs and a pair of antennae. Fire ants of those species invasive in the United States can be distinguished from other ants locally present by their copper brown head and thorax with a darker abdomen. The worker ants are blackish to reddish and their size varies from 2 to 6 mm (0.079 to 0.236 in). In an established nest these different sizes of ants are all present at the same time.[4]
Solenopsis spp. ants can be identified by three body features—a pedicel with two nodes, an unarmed propodeum, and antennae with 10 segments plus a two-segmented club.[5] Many ants bite, and formicine ants can cause irritation by spraying formic acid; myrmecine ants like fire ants have a dedicated venom-injecting sting, which injects an alkaloid venom, as well as mandibles for biting.[6]
A typical fire ant colony produces large mounds in open areas, and feeds mostly on young plants and seeds. Fire ants often attack small animals and can kill them. Unlike many other ants, which bite and then spray acid on the wound, fire ants bite only to get a grip and then sting (from the abdomen) and inject a toxic alkaloid venom called solenopsin, a compound from the class of piperidines. For humans, this is a painful sting, a sensation similar to what one feels when burned by fire (hence the name), and the after-effects of the sting can be deadly to sensitive people.[7] Fire ants are more aggressive than most native species, so have pushed many species away from their local habitat. One such species that Solenopsis ants parasitically take advantage of are bees, such as Euglossa imperialis, a nonsocial orchid bee species, from which the ants enter the cells from below the nest and rob the cell’s contents.[8] These ants are renowned for their ability to survive extreme conditions. They do not hibernate, but can survive cold conditions, although this is costly to fire ant populations as observed during several winters in Tennessee, where 80 to 90% of colonies died due to several consecutive days of extremely low temperatures.[9]
