Most of these ants are native to Australia; others are found in Asia and Oceania, and they have been introduced to Brazil, New Zealand, and the United Arab Emirates.

Meat ants also engage in ritualised fighting, which helps prevent casualties and solve territorial disputes between neighbouring colonies.

Ants of the genus live in a wide variety of habitats and nest in soil in numbers that range from a few hundred individuals to over 300,000 in a single colony.

Some species associate with caterpillars and butterflies that provide the ants with secretions and honeydew, and I. bicknelli pollinates orchids.

The separation of the genus Iridomyrmex from its most recent common ancestor began around 12 million years ago.

[4] In comparison to other Indo-Australian genera in the subfamily Dolichoderinae, the clade of which it is a part, is 23 million years old, meaning that it is rather young.

[12] The scientific name of the genus, Iridomyrmex, meaning "rainbow ant", refers to their blue-green iridescent sheen.

[15] [extinct species are marked with †] Unlike other genera in Dolichoderinae, the front margin of the clypeus is not below the mandibles; instead, it is located above them.

In the Oceanian region, these ants are found in Fiji, Indonesia, New Caledonia, Papua New Guinea and the Solomon Islands.

[4][23] I. anceps is the only known ant of this genus present in the Middle East, having been introduced to the United Arab Emirates.

[4] Extinct species were native to a range spanning beyond the modern distribution of the genus; fossils have been found in China, France and the United States.

[5] Most of these ants nest in soil, but some prefer to live under rocks, rotten wood, and in some cases in sandy beaches and footpaths.

[4] Some colonies are known to create "super-nests": workers construct many nests connected through established paths, extending up to 650 metres (2,130 ft) in length.

[16] In one extreme case, a single colony was found to occupy over 10 hectares of land with 85 individual nests and 1,500 entrance holes.

[4] Even smaller species show similar behaviours to these ants and will also swarm out of their nests to bite and spray iridomyrmecin, a defensive chemical found in the genus.

[32] Because of their large numbers, aggression, and activeness, Iridomyrmex ants are ecologically dominant in Australia, and several species are known to obtain exclusive possession to food sources and prevent other insects from using them.

[4] Meat ants engage in ritualised fights to maintain and resolve boundary disputes with neighbouring colonies.

[34] Such disputes between colonies may continue for months or even years in the same area, and escalated fights that result in serious injury or death are rare.

[4] Workers forage and scavenge for small insects, and they collect nectar from flowers and hunt for prey.

In a few species, a nest will not be placed in a shaded area; this is so it can warm up during the early mornings and workers can forage shortly after sunrise.

The seedlings that sprout from these seeds benefit from proximity to the aggressive Iridomyrmex ants, giving them a better chance of survival.

[50] A prominent predator is the short-beaked echidna (Tachyglossus aculeatus) that eats the virgin queens during nuptial flight due to their high percentage of fat.

Finding a location to nest is dangerous, as birds and other ants prey on them;[56] disease and starvation are other causes of death in queens.

[66]: 288  I. bicknelli is an effective pollinator of Microtis parviflora,[68] and one study suggests the pollen is not harmed by contact of these ants.

[73] In rural Australia, meat ants are important to farmers as they place animal carcasses on their nests.

[77] Particular species have adapted rather well to urbanisation; during the early days in Canberra, newly constructed suburbs provided new nest sites for meat ants, and populations flourished.