Iridomyrmex

The separation of the genus Iridomyrmex from its most recent common ancestor began around 12 million years ago. Its sister group, Froggattella, has only two species, even though both genera are the same age. 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. However, the fossil species that have been found are from the Eocene and Oligocene. The following cladogram shows the phylogenetic position of Iridomyrmex among the Indo-Australian genera: }} ==Taxonomy==

The genus Iridomyrmex was first described by Austrian entomologist Gustav Mayr in 1862, but it had no designated type species until 1903. By then, the type species was designated as Formica detecta, a synonym of Iridomyrmex purpureus. The genus was placed in the subfamily Dolichoderinae in 1878, the same year the subfamily was established. Since the establishment of the genus, it suffered taxonomic misunderstanding due to the gradual development of unrelated ants being designated into the genus by early researchers who failed to identify features that would make them distinct from the genus Iridomyrmex. Myrmecologist William Brown Jr., was perhaps the first person to question the monophyly of the genus, The first proper revisions of the genus began in the 1990s, and 91 species were transferred to six genera; only 62 species remained after these revisions. The scientific name of the genus, Iridomyrmex, meaning "rainbow ant", refers to their blue-green iridescent sheen. The word Irido, meaning "rainbow", derives from Ancient Greek, and myrmex, another Greek word, means "ant". Species [extinct species are marked with †] • Iridomyrmex adstringatus Heterick & Shattuck, 2011 • Iridomyrmex agilis Forel, 1907 • Iridomyrmex alpinus Heterick & Shattuck, 2011 • Iridomyrmex anceps (Roger, 1863) • Iridomyrmex anderseni Shattuck, 1993 • Iridomyrmex angusticeps Forel, 1901 • Iridomyrmex anteroinclinus Shattuck, 1993 • Iridomyrmex atypicus Heterick & Shattuck, 2011 • Iridomyrmex azureus Viehmeyer, 1914 • Iridomyrmex bicknelli Emery, 1898 • Iridomyrmex bigi Shattuck, 1993 • Iridomyrmex brennani Heterick & Shattuck, 2011 • †Iridomyrmex breviantennis Théobald, 1937 • Iridomyrmex brunneus Forel, 1902 • Iridomyrmex calvus Emery, 1914 • Iridomyrmex cappoinclinus Shattuck, 1993 • Iridomyrmex cephaloinclinus Shattuck, 1993 • Iridomyrmex chasei Forel, 1902 • Iridomyrmex coeruleus Heterick & Shattuck, 2011 • Iridomyrmex conifer Forel, 1902 • Iridomyrmex continentis Forel, 1907 • Iridomyrmex cuneiceps Heterick & Shattuck, 2011 • Iridomyrmex cupreus Heterick & Shattuck, 2011 • Iridomyrmex curvifrons Heterick & Shattuck, 2011 • Iridomyrmex cyaneus Wheeler, 1915 • Iridomyrmex difficilis Heterick & Shattuck, 2011 • Iridomyrmex discors Forel, 1902 • Iridomyrmex dromus Clark, 1938 • Iridomyrmex elongatus Heterick & Shattuck, 2011 • Iridomyrmex exsanguis Forel, 1907 • †Iridomyrmex florissantius Carpenter, 1930 • Iridomyrmex fulgens Heterick & Shattuck, 2011 • Iridomyrmex galbanus Shattuck, 1993 • Iridomyrmex gibbus Heterick & Shattuck, 2011 • Iridomyrmex gumnos Heterick & Shattuck, 2011 • Iridomyrmex hartmeyeri Forel, 1907 • Iridomyrmex hertogi Heterick & Shattuck, 2011 • Iridomyrmex hesperus Shattuck, 1993 • Iridomyrmex infuscus Heterick & Shattuck, 2011 • Iridomyrmex innocens Forel, 1907 • Iridomyrmex lividus Shattuck, 1993 • Iridomyrmex longisoma Heterick & Shattuck, 2011 • Iridomyrmex luteoclypeatus Heterick & Shattuck, 2011 • Iridomyrmex macrops Heterick & Shattuck, 2011 • †Iridomyrmex mapesi Wilson, 1985 • Iridomyrmex mattiroloi Emery, 1898 • Iridomyrmex mayri Forel, 1915 • Iridomyrmex meridianus Heterick & Shattuck, 2011 • Iridomyrmex minor Forel, 1915 • Iridomyrmex mirabilis Heterick & Shattuck, 2011 • Iridomyrmex mjobergi Forel, 1915 • Iridomyrmex neocaledonica Heterick & Shattuck, 2011 • Iridomyrmex niger Heterick & Shattuck, 2011 • Iridomyrmex nudipes Heterick & Shattuck, 2011 • †Iridomyrmex obscurans Carpenter, 1930 • Iridomyrmex obscurior Forel, 1902 • Iridomyrmex obsidianus Emery, 1914 • Iridomyrmex omalonotus Heterick & Shattuck, 2011 • Iridomyrmex pallidus Forel, 1901 • Iridomyrmex phillipensis Heterick & Shattuck, 2011 • Iridomyrmex prismatis Shattuck, 1993 • Iridomyrmex purpureus (Smith, 1858) • Iridomyrmex reburrus Shattuck, 1993 • Iridomyrmex roseatus Heterick & Shattuck, 2011 • Iridomyrmex rubriceps Forel, 1902 • Iridomyrmex rufoinclinus Shattuck, 1993 • Iridomyrmex rufoniger (Lowne, 1865) • Iridomyrmex sanguineus Forel, 1910 • Iridomyrmex setoconus Shattuck & McMillan, 1998 • †Iridomyrmex shandongicus Zhang, 1989 • Iridomyrmex spadius Shattuck, 1993 • Iridomyrmex splendens Forel, 1907 • Iridomyrmex spodipilus Shattuck, 1993 • Iridomyrmex spurcus Wheeler, 1915 • Iridomyrmex suchieri Forel, 1907 • Iridomyrmex suchieroides Heterick & Shattuck, 2011 • Iridomyrmex tenebrans Heterick & Shattuck, 2011 • Iridomyrmex tenuiceps Heterick & Shattuck, 2011 • Iridomyrmex trigonoceps Heterick & Shattuck, 2011 • Iridomyrmex turbineus Shattuck & McMillan, 1998 • Iridomyrmex victorianus Forel, 1902 • Iridomyrmex viridiaeneus Viehmeyer, 1914 • Iridomyrmex viridigaster Clark, 1941 • Iridomyrmex xanthocoxa Heterick & Shattuck, 2011 ==Description==

Unlike other genera in Dolichoderinae, the front margin of the clypeus is not below the mandibles; instead, it is located above them. The eyes are located on top of the ants' head, and they are noticeably distant from the mandibles. Worker castes are rarely polymorphic. ==Distribution and habitat==

Ants of this genus are found in a range spanning several continents. In the Oceanian region, these ants are found in Fiji, Indonesia, New Caledonia, Papua New Guinea and the Solomon Islands. In Australia, they are found in every state and territory. In New Zealand, this genus has been introduced to the country, establishing themselves in both the North Island and South Island. In Asia, they are found in Burma, East Timor, India, Malaysia and the Philippines. I. anceps is the only known ant of this genus present in the Middle East, having been introduced to the United Arab Emirates. I. rufoniger was introduced to Brazil through human activity. Populations are present on the islands of Norfolk Island and Phillip Island in Oceania. mound near Bungendore, New South Wales The genus Iridomyrmex inhabits rural, arid, and semi-arid areas. Nests will vary in appearance; most species live in small mounds with a single entrance, while other species create large mounds covered in pebbles with multiple entrances. While meat ants are never aggressive to their nest mates, they will be aggressive to those who live in different nests within the same colony. Nests may be above or below ground, with some species such as I. conifer alternating between the two; during winter, nests will be constructed above in twigs, with the ants moving back underground during the warmer months. ==Behaviour and ecology==

Most Iridomyrmex species are aggressive ants that will attack anything which attacks or disturbs their nests or trails they forage on. This is noticeable with particular member species of the I. purpureus species group, where they will pour out of their nest and attack and kill all intruders. 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. These ants will also affect foraging behaviours of other ant nests living nearby due to how active they are and their large numbers. When individuals from separate colonies meet, they will engage each other until appeasement occurs. A meat ant detects a foreign worker by intense antennation and gaping of the mandibles, and will also stretch themselves upward to appear taller and larger, suggesting that meat ants do this in a display of size matching. Diet Iridomyrmex primarily feeds on sweet foods such as nectar and honeydew. Colonies sometimes nest in termite mounds, and so the termites are regularly preyed on by Iridomyrmex; no evidence for any kind of relationship (other than a predatory one) is known. as certain Iridomyrmex species such as I. purpureus and I. ruburrus are immune to the toxins released by the cane toads. As a result, placing Iridomyrmex nests in habitats which house cane toads have been suggested as a method of controlling the cane toad population. The meat ant is the only known ant in Australia that feeds on guano. Predators Some invertebrate species specialise in predation of Iridomyrmex ants. One spider in particular, the cursorial spider Habronestes bradleyi, is a specialist predator against these ants and will use the alarm pheromones that are released by the ants during territorial disputes to locate them. The Australian thorny devil lizard (Moloch horridus) is a sit and wait predator that primarily preys on Iridomyrmex ants, and one lizard will reject specific species in this genus while eating others. The blind snake Ramphotyphlops nigrescens follows trails laid by these ants to locate them as a potential prey species and will eat the broods of some species, while ground beetles dig burrows near ant nests to prey on workers passing by. 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. Echidnas do not consume Iridomyrmex ants all year; instead, they usually attack nests during August to October, which is when the winged females and males, known as alates emerge from their nest. Queens will also face more threats during nuptial flight or after; birds such as currawongs, magpies and ravens, attracted by recently excavated soil, will dig out nests shortly after the queens have founded their colonies. Parasitic flatworms in the class Cestoda are known to infect Iridomyrmex. Life cycle and reproduction Nuptial flight occurs throughout the year in humid and warm climates. Mature nests range in size, from a few hundred to over 300,000 workers. Oligogynous colonies also exist, in which multiple queens are present, but they are tolerated equally by workers birthed from different mothers and antagonism exists among queens. Brood discrimination is known based on recognition of kin, and queens will look after their own brood and neglect other brood laid by different queens. Queens display intolerance to each other when the first generation of workers is present, and the queens will separate from each other once the colony grows to a certain size. ==Symbiosis==

Iridomyrmex ants share symbiotic relationships with many caterpillars, aphids and coccids. Workers protect these caterpillars and will sometimes take them to their feeding chambers inside the nest. In the genus Jalmenus, workers attend to the butterflies Jalmenus clementi (turquoise hairstreak), Jalmenus daemeli (emerald hairstreak), Jalmenus eichhorni (northern hairstreak),Jalmenus evagoras (imperial hairstreak) Jalmenus icilius (amethyst hairstreak), Jalmenus inous (varied hairstreak) and Jalmenus lithochroa (Waterhouse's hairstreak). In the genus Ogyris, attendants include Ogyris amaryllis (satin azure), Ogyris olane (olane azure) and Ogyris oroetes (silky azure). and one study suggests the pollen is not harmed by contact of these ants. Meat ants have been observed blocking banded sugar ant nesting holes with pebbles and soil to prevent them from leaving their nest during the early hours of the day. The ants counter this by preventing meat ants from leaving their nest by blocking their nesting holes with debris, a behaviour known as nest-plugging. If meat ant nests are encroached by trees or other shade, banded sugar ants may invade and take over the nest, since the health of the colony may deteriorate from overshadowing. Members of an affected meat ant colony later move to a nearby satellite nest that is placed in a suitable area, while invading banded sugar ants fill nest galleries up with a black resinous material. ==Interaction with humans==

In rural Australia, meat ants are important to farmers as they place animal carcasses on their nests. In a matter of weeks, the entire carcass will be consumed and reduced to bones. However, Iridomyrmex ants are sometimes considered pests, due to these ants entering human houses to feed on food and soil disturbance. Eradication of nests can be difficult, as nests can be repopulated from a rival colony or adjoining nests which were not affected. 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. Other factors include plantations enriched with valuable food sources and home gardens. Workers also cause problems for those who are Citrus producers; they will affect the biological control of Hemiptera insects, specifically those who produce honeydew. ==See also==