Meat ant

The meat ant (Iridomyrmex purpureus), also known as the gravel ant or southern meat ant, is a species of ant endemic to Australia. A member of the genus Iridomyrmex in the subfamily Dolichoderinae, it was described by British entomologist Frederick Smith in 1858. The meat ant is associated with many common names due to its appearance, nest-building behaviour and abundance, of which its specific name, purpureus, refers to its coloured appearance. It is among the best-known species of ant found throughout Australia; it occurs in almost all states and territories except for Tasmania. Its enormous distribution, aggression and ecological importance have made this ant a dominant species. The meat ant is monomorphic (occurs in a particular form), although there is evidence that certain populations can be polymorphic. It is characterised by its dark-bluish body and red head. It is a medium to large species, measuring 6–12 mm (0.24–0.47 in). The workers and males are approximately the same sizes at 6–7 mm (0.24–0.28 in) and 8 mm (0.31 in), respectively. The queens are the largest and appear mostly black, measuring 12.7 mm (0.50 in). The iridescence in workers ranges from green or blue to plain green and purple, varying in different body parts and castes. Meat ants inhabit open and warm areas in large, oval-shaped mounds that are accompanied by many entrance holes. The nest area is always cleared of vegetation and covered with materials including gravel, pebbles and dead vegetation. They are also polydomous, where a colony may be established in a series of satellite nests connected by well-defined paths and trails. Satellite nests are constructed away from the main nest in nearby areas with valuable food sources so workers can exploit them. Queens mate with a single male and colonies may have more than one queen until the workers arrive, where they both exhibit antagonism. It takes around one or two months for an individual egg to develop into an adult. Colonies range in size, varying between 11,000 individuals to over 300,000. The meat ant is a diurnal species (active throughout most of the day), especially when it is warm. It forages on trees and collects sweet substances such as honeydew and nectar, and also captures insects or collects the remains of animals. A number of predators eat these ants, including the short-beaked echidna (Tachyglossus aculeatus), numerous species of birds, blind snakes and spiders. This species is also a competitor of the banded sugar ant (Camponotus consobrinus). Meat ants establish territorial borders with neighbouring colonies and solve disputes through ritualised fighting. Meat ants play an important role in both the environment and for humans. A single nest is capable of dispersing over 300,000 plant seeds; moreover, meat ants have formed symbiotic relationships with many insects. This ant may be used as a form of pest control to kill the cane toad, an invasive species. They can also help farmers to remove animal carcasses by consuming and reducing them to bones in a matter of weeks. Despite this, meat ants are sometimes pests around urban areas and eradicating them is difficult.

Taxonomy

The meat ant was first described in 1858 by British entomologist Frederick Smith in his Catalogue of Hymenopterous Insects in the Collection of the British Museum part VI, under the binomial name Formica purpurea from a holotype worker ant he collected in Melbourne, Victoria. The type material is currently housed in the Natural History Museum, London. In 1862, Austrian entomologist Gustav Mayr erected the genus Iridomyrmex, and reclassified the meat ant as a member of Iridomyrmex rather than the genus Formica. The ant was named Iridomyrmex purpurea in 1862. Mayr renamed the ant as Iridomyrmex purpureus one year after. I. purpureus was later classified as a synonym of Iridomyrmex detectus, and this taxon was designated as the type species of Iridomyrmex in 1903. In 1993, I. detectus was synonymised with I. purpureus and grouped into the I. purpureus species complex. I. detectus was described as a separate species by Smith the same year as I. purpureus from two syntype queens he collected from the Hunter River in New South Wales. Although the name I. purpureus was used by many authors, Karl Wilhelm von Dalla Torre reused I. detectus and this was adopted by several authors, replacing I. purpureus. By the 1960s I. purpureus once again became preferred over I. detectus. While the two names were described in the same year and publication, the name I. purpureus is the valid name for the species in accordance with the International Code of Zoological Nomenclature. Entomologist B.T. Lowne was the first person to revise I. purpureus and I. detectus, and he synonymised the two species. Several synonyms have either been classified as a separate species from the meat ant or even a subspecies. Iridomyrmex purpureus sanguineus and I. p. viridiaeneus were classified as subspecies in 1974, previously being recognised as two species. I. detectus castrae was originally described as a variant of the meat ant in 1925 (as I. d. var. castrae), but the taxon was reclassified as a subspecies in 1985; subsequently, a 1993 revision reclassified I. p. sanguineus and I. p. viridiaeneus at species level while I. d. castrae was synonymised, based on morphological examinations of collected material. Camponotus horni, Formica smithii and Liometopum aeneum were described as three distinct species in three different ant genera, but these classifications were short-lived, as scientists discovered that these taxa were all identical, and subsequently synonymised them with the meat ant. Camponotus horni was described by English entomologist William Forsell Kirby in 1896 from worker and queen syntypes he collected at Palm Creek in the Northern Territory. In 1930, Australian entomologist John S. Clark reviewed these specimens and synonymised the taxon with the meat ant. However, the queen was later found to be distinct from the workers and C. horni was redescribed as a species. The information provided by Clark makes it sufficient to retain the validity of the name, making Clark the new author of C. horni. The taxonomic status of Clark's C. horni was uncertain and remained a junior homonym for Kirby's C. horni, until American entomologist Brian Fisher renamed Clark's C. horni to Camponotus durnyx in 2025.

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