Back to Dolichoderinae
Iridomyrmex is one of the largest
and most frequently encountered groups of ants in Australia.
They are also one of the most ecologically important groups as
they interact strongly with many other invertebrates as well as many plants.
Iridomyrmex species frequently form large
nests which are patrolled by aggressive workers. This can significantly reduce the number of
other species which can nest or forage in the vicinity. Sometimes the only species which can co-exist with Iridomyrmex are those which forage at different
times of the day or differ in size compared with Iridomyrmex species, and thus “escape” interactions with the Iridomyrmex workers.
aggressive actions of Iridomyrmex species are not just limited to other species of ants.
Individual colonies of the same and closely related meat ants (Iridomyrmex
purpureus group) form discrete, non-overlapping territories with well-defined
boundaries. These boundaries are
patrolled regularly and when disputes arise, ritualised fighting can occur.
During these fights, large numbers of workers from each colony
come together, stand upright on the tips of their legs and kick each other
with their hind legs. These confrontations can go on for hours or even days with little
or no mortality among the combatants.
Once the boundary dispute has been resolved, the workers return
to their nests and little interaction is seen in the former battlefield.
Iridomyrmex associate closely
with the caterpillars of certain butterflies. In extreme cases, the caterpillars live in
the nests of Iridomyrmex and
are carried to feeding areas and protected by the ants. The caterpillars
have special glands that produce secretions which are very attractive
to these ants.
of invertebrates have taken advantage of the large nests of Iridomyrmex
by becoming specialist predators on these ants.
Some spiders prey largely on Iridomyrmex
workers, and have even developed the ability to use the ants’ communication
chemicals to determine which individuals to attack. The ants release a special chemical when injured to alert other
ants of potential danger. The
spiders detect this chemical and preferentially select these injured workers
as potential prey. Some predacious
ground beetles establish their burrows in soil near the ants’ nests. From the relative safety of their burrows,
they grab passing ants and kill them, feeding on their body fluids.
plants produce seeds with special food bodies (elaiosomes) that are attractive
to ants and other insects. Iridomyrmex
foragers are often attracted to these seeds and carry them into their
nests. Once the food bodies are
taken from the seeds, the seeds are discarded.
Being in or near the ants’ nests provides protection to the young
seedlings and may increase the survival of the plants.
are located in soil, with or without covering, and range in size from
a few hundred to over 300,000 workers. The above-ground structure of nests varies
from large mounds decorated with small pebbles and having many entrances
to single, cryptic holes just large enough for individual workers to squeeze
through. Several species in southern
Western Australia (in the Iridomyrmex conifer species group) alternate
between two distinct nest types. In the cool winter months they construct above
ground twig nests in open areas, while in the hot summer months they move
to below ground nests in shaded areas.
Colonies of meat ants (Iridomyrmex
purpureus group) are often spread over wide areas with many individual
nests connected by well defined paths.
In some cases these “super nests” can stretch up to 650 metres.
species of Iridomyrmex are general
scavengers. They may also tend
aphids and coccids and will collect nectar when available. Workers of some forage in large, well defined
columns to the same feeding sites for extended periods of time, while
others forage singly.
literature concerning these ants is extensive.
A few of the more significant papers include those by Andersen
and Patel (1994), Briese and Macauley (1981), Clayton-Green and Ashton
(1990), Ettershank (1971), Ettershank and Ettershank (1982), Greenslade
(1974, 1979), Greenslade and Halliday (1982), Moore (1974) and Shattuck
(1992, 1993a, 1993b, 1996).
Distribution and Habitats
The 79 described species and subspecies of Iridomyrmex are distributed from India
east to China and south to Australia and New Caledonia. An additional seven species are known from
fossil records. Within Australia,
63 species and subspecies are described.
They occur in all areas (see map) and all major habitats, often
in large numbers and with many species at any given site.
Members of this genus can be identified by having the front margin of
the clypeus above the mandibles highly modified with convex areas towards
the sides and a central projection (this central projection varies from
strongly to weakly developed) (Figs 1a, 2).
In addition, the compound eyes are placed relatively high on the
head and away from the mandibles (Figs 1b, 2). Most other genera in the subfamily Dolichoderinae
have the front margin of the clypeus weakly convex, straight or weakly
concave. Only Froggattella
share the central projection with Iridomyrmex,
but these have the eyes low on the head, nearer to the clypeus and Froggattella
has the propodeal spiracle higher and on the propodeal spines.
of Iridomyrmex form "highways" between their nests and
favorite feeding areas. These highways are warn smooth by the action of
thousands of tarsii marching over them day after day, month after month.
In this case the roadway runs from an Iridomyrmex purpureus nest
(upper right) towards a food source in a Eucalyptus tree located
some 9m away (to the lower left). (Photo by Steve Shattuck.)
are highly efficient predators/scavangers, taking a wide range of prey
as food for their larvae. These workers have found a queen Aphaenogaster
which is being returned intact to their nest (upper right). It will then
be broken into sections small enough to fit through the nest entrance
before being take to the brood chambers. (Photo by Steve Shattuck.)
Crozier 1968 (karyotypes
of the I. purpureus group), Ettershank 1971 (ecology), Greenslade
1974 (ecology), Moore 1974 (predation by Coleoptera), Briese and Macauley
1981 (biology), Ettershank and Ettershank 1982 (behaviour), Greenslade
and Halliday 1982 (taxonomy and speciation in the I. purpureus
group), Brophy et al. 1983 (biochemistry), Greenslade and Halliday 1983
(ecology of the I. purpureus group), Pierce 1984 (association
with Lepidoptera), Fox et al. 1985 (ecology), Pierce and Elgar 1985
(association with Lepidoptera), Greenslade 1987 (ecology of the I.
purpureus group), Pierce et al. 1987 (association with Lepidoptera),
Haering and Fox 1987 (ecology), Elgar and Pierce 1988 (association with
Lepidoptera), Clayton-Greene and Ashton 1990 (ecology), Shattuck 1992
(generic status), Shattuck 1993a (revision of the I. purpureus
group), Shattuck 1993b (revision of the I.calvus group), Andersen
and Patel 1994 (ecology), Shattuck 1996 (revision of the I. discors
group), Shattuck and McMillan 1998 (revision of the I. conifer
1862:702. Type species: Formica purpurea F. Smith, designated
by Bingham 1903:297.
Go to the Taxonomic
Catalogue of Species.
Cited / Additional Reading
Andersen, A. N., Patel,
A. D. 1994. Meat ants as dominant members of Australian ant communities:
an experimental test of their influence on the foraging success and
forager abundance of other species. Oecologia (Berlin). 98 : 15–24.
Briese, D. T., Macauley, B. J. 1981. Food collection within an
ant community in semi-arid Australia, with special reference to seed
harvesters. Australian Journal of Ecology. 6 : 1–19.
Brophy, J. J., Cavill, G. W. K., Davies, N. W., Gilbert, T. D., Philp,
R. P., Plant, W. D. 1983. Hydrocarbon constituents of three species
of dolichoderine ants. Insect Biochemistry. 13 : 381–390.
Clayton-Greene, K. A., Ashton, D. H. 1990. The dynamics of Callitris
columellaris/Eucalyptus albens communities along the Snowy
River and its tributaries in South-eastern Australia. Australian Journal
of Botany. 38 : 403–432.
Crozier, R. H. 1968. Interpopulation karyotype differences in
Australian Iridomyrmex of the "detectus" group (Hymenoptera:
Formicidae: Dolichoderinae). Journal of the Australian Entomological
Society. 7 : 25–27.
Elgar, M. A., Pierce, N. E. 1988. Mating success and fecundity
in an ant-tended lycaenid butterfly, pp. 59-75. In T. H. Clutton-Brock
(ed.) : studies of individual variation in contrasting breeding systems.
University of Chicago Press. Chicago. pp.
Ettershank, G. 1971. Some aspects of the ecology and nest microclimatology
of the meat ant, Iridomyrmex purpureus (Sm.). Proc. R. Soc. Victoria.
84 : 137–151.
Ettershank, G., Ettershank, J. A. 1982. Ritualised fighting in
the meat ant Iridomyrmex purpureus (Smith) (Hymenoptera: Formicidae).
Journal of the Australian Entomological Society. 21 : 97–102.
Fox, B. J., Fox, M. D., Archer, E. 1985. Experimental confirmation
of competition between two dominant species of Iridomyrmex (Hymenoptera:Formicidae).
Australian Journal of Ecology. 10 : 105–110.
Greenslade, P. J. M. 1974. Some relations of the meat ant, Iridomyrmex
purpureus (Hymenoptera: Formicidae) with soil in South Australia.
Soil Biology and Biochemistry. 6 : 7–14.
Greenslade, P. J. M. 1987. Environment and competition as determinants
of local geographical distribution of five meat ants, Iridomyrmex
purpureus and allied species (Hymenoptera: Formicidae). Australian
Journal of Zoology. 35 : 259–273.
Greenslade, P. J. M., Halliday, R. B. 1982. Distribution and
speciation in meat ants, Iridomyrmex purpureus and related species
(Hymenoptera: Formicidae). pp. 249–255 in Barker, W. R., Greenslade,
P. J. M. Evolution of the flora and fauna of arid Australia. Frewville,
South Australia : Peacock Publications. 392 pp. Greenslade, P. J. M.,
Halliday, R. B. (1983). Colony dispersion and relationships of meat
ants Iridomyrmex purpureus and allies in an arid locality in
South Australia. Insectes Sociaux. 30 : 82–99.
Haering, R., Fox, B. J. 1987. Short-term coexistence and long-term
competitive displacement of two dominant species of Iridomyrmex:
The successional response of ants to regenerating habitats. Journal
of Animal Ecology. 56 : 495–507.
Moore, B. P. 1974. The larval habits of two species of Sphallomorpha
Westwood (Coleoptera: Carabidae, Pseudomorphinae). Journal of the Australian
Entomological Society. 13 : 179–183.
Pierce, N. E. 1984. Amplified species diversity: a case study
of an Australian lycaenid butterfly and its attendant ants. Pp. 197-200
in R. I. Vane-Wright and P. Ackery (eds.) The Biology of Butterflies.
xxv + 429 pp. Academic Press, London.
Pierce, N. E., Elgar, M. A. 1985. The influence of ants on host
plant selection by Jalmenus evagoras, a myrmecophilous lycaenid
butterfly. Behavioral Ecology and Sociobiology. 16 : 209–222.
Pierce, N. E., Kitching, R. L., Buckley, R. C., Taylor, M. F. J.,
Benbow, K. F. 1987. The costs and benefits of cooperation between
the Australian lycaenid butterfly, Jalmenus evagoras, and its
attendant ants. Behavioral Ecology and Sociobiology. 21 : 237–248.
Shattuck, S. O. 1992. Review of the dolichoderine ant genus Iridomyrmex
Mayr with descriptions of three new genera (Hymenoptera: Formicidae).
Journal of the Australian Entomological Society. 31 : 13–18.
Shattuck, S. O. 1993a. Revision of the Iridomyrmex purpureus
species group (Hymenoptera: Formicidae). Invert. Tax. 7: 113-149.
Shattuck, S. O.
1993b. Revision of the Iridomyrmex calvus species-group (Hymenoptera:
Formicidae). Invertebrate Taxonomy. 7 : 1303–1325 .
Shattuck, S. O. 1996. Revision of the Iridomyrmex discors
species-group (Hymenoptera: Formicidae). Aust. J. Entomol. 35 : 37–42.
Shattuck, S.O. & McMillan, P. 1998. Revision of the species of
the Iridomyrmex conifer group (Hymenoptera : Formicidae), with
notes on their biology. Australian Journal of Zoology. 46 : 301–315.