Fire ants bite only to hold on, then sting with an alkaloid venom
Fire ants belong to Solenopsis, a genus of more than two hundred stinging species. Their name comes from a sting that feels like a burn, delivered after they clamp on with their jaws, and in sensitive people the effects can be deadly. They also shrug off harsh conditions that would kill many other ants.
Common names cause confusion. Terms like ginger ant or red ant are applied loosely, and none covers all Solenopsis species or only them. Myrmica rubra and Pogonomyrmex barbatus are often called red ants, the unrelated weaver ants of Southeast Asia get called fire ants for their colour and painful bite, and Wasmannia auropunctata is known as the little fire ant. Specialists instead look for three features: a waist of two nodes, a spineless propodeum, and ten-segmented antennae ending in a two-part club.
Workers are blackish to reddish and range from 2 to 6 millimetres, with every size present in a mature nest. The invasive species in the United States stand out for a copper-brown head and thorax above a darker abdomen. Unlike formicine ants, which spray formic acid, fire ants carry a true sting that injects solenopsin, a piperidine alkaloid. Colonies eat mostly young plants, seeds and insects, and can kill small animals such as lizards. They also raid the orchid bee Euglossa imperialis, breaking into its brood cells from below to steal the contents, and their aggression has driven many native ant species out.
Some relationships are cooperative. Larvae of the butterfly Lycaena rubidus ooze a sugary fluid, and fire ants carry them home and guard them through pupation in return for the food. With Eurybia elvina, the ants build soil shelters over older caterpillars on flower heads.
Nests sit in soil, often near water such as riverbanks, ponds, watered lawns and road verges, usually hidden under logs, rocks or bricks. Without cover they raise dome-shaped mounds in open ground that commonly reach 40 centimetres and on heavy soils can stand a metre high and 1.5 metres across. One queen or a small group founds a colony, which can reach thousands within about a month, and some nests have several queens. Fire ants do not hibernate, but cold still takes a toll: in Tennessee, runs of freezing days during several winters killed 80 to 90 percent of colonies.
Source: Fire ant
