There are about 60 species of Iridomyrmex in Australia. They often build large nests underground with sand or gravel mounded around the entrances to the nest. Iridomyrmex species are often involved in mutually beneficial (symbiotic) relationships with caterpillars. The caterpillars provide sugary fluid for the ants in return from protection from predators. Workers have strong jaws - they do not sting but can give a painful bite.