The typical ant nest begins
with a single individual, the queen. This queen flew from her home
nest a day or two earlier, together with other queens and males from
her nest and other nests in the area. The queen searches for a mate,
often being attracted to large, distinctive objects such as especially
tall trees, large shrubs or hill tops. These sites act as meeting
places for queens and males from many nests, ensuring that they can
find each other. The queen then mates with one or a few males while
still in the air or on low vegetation or the ground. Once mated, she
searches for a suitable nest site. Where she searches will vary with
the species and can range from the tops of trees to open soil.
Either during her search
or once a suitable site is found she bites off her wings as they are
no longer needed. She then seals herself into a small chamber or other
secluded place and lays a small batch of eggs. The queen remains in
the nest with her brood while it develops, feeding the growing larvae
special trophic (unfertilised) eggs which she lays specifically as
food for them. These first workers (called nanitics) are often much
smaller than subsequent workers as the queen can only provide a limited
amount of food compared to that which foraging workers can provide.
Once these initial workers mature, they leave the nest and begin to
forage, returning captured prey to the queen and her additional brood.
The colony grows as more
workers mature, these new workers taking over the care of brood as
well as bringing in additional food. At this stage, the queen reduces
her activities to egg laying and the workers assume all other tasks
in the nest. The queen is still essential for normal colony life,
however, as the chemical messages she produces controls the activities
of all workers in the nest.
The above pattern of nest
founding is one of the most common and widespread, however many species
vary from it. For example, in some
Rhytidoponera
mating may take place on or in existing nests (Haskins 1978 and Ward
1981). It is also common for several queens to establish a nest together
and then either live together or later fight among themselves to determine
which queen remains in the nest, the others being forced out or killed
(for example, in
Oecophylla,
see Peeters and Andersen 1989). In other species, new colonies are
established when a new queen leaves an existing nest together with
a number of workers and relocates to a new location some distance
away (as in
Aenictus,
see Wilson 1964).
Queens may forage outside
the nest before the first workers emerge (in
Nothomyrmecia,
see Hölldobler and Taylor 1984). They may remain in their parental
nests or form small satellite nests which share workers with the main
nest (
Oecophylla
(Hölldobler and Wilson 1983) and some
Iridomyrmex
(Holldobler and Carlin 1985)). In others, brood may be removed from
the main nest and placed in small groups together with a few workers
near food sources (
Amblyopone).
The specific details of nest founding is as varied as the ants themselves.
For a more comprehensive discussion, see Hölldobler and Wilson
(1990).
As the colony reaches maturity,
it begins to produce the queens and males (called alates) which will
form the next generation. Numerous factors determine when queens are
produced, including the time of year, the food available to the growing
larvae, the size and contents of the egg laid, pheromones or hormones
produced by the queen and the age of the queen. The production of
males has a much simpler controlling mechanism. As it turns out, females
(queens and workers) are diploid. That is, they have two copies of
each chromosome. Males, on the other hand, are haploid and have only
a single copy of each chromosome. Because of this, fertilised eggs,
where an egg and sperm combine, form females while unfertilised eggs
develop into males. These factors combine to give the colony a high
degree of control over when queens and males are produced, as well
as the relative numbers of each.
The larvae of these new
queens and males are similar to the larvae of workers but are generally
larger. Once they emerge, they remain in the nest waiting for environmental
triggers to initiate their leaving the nest. These same triggers will
cause the simultaneous release of queens and males from the vast majority
of nests of a given species in a given area. Because of this, huge
numbers of queens and males can be released on the same day, sometimes
over hundreds of kilometres. In open country with scattered shrubs,
large numbers of flying ants can be seen hovering over each shrub
over wide areas. These mass emergences last only a few days, with
the queens mating and attempting to establish new nests while the
males generally die within several days of leaving their nests.
Once established, individual
nests can last many years. Queens of the common "sugar ant"
of south-eastern Australia,
Camponotus consobrinus, have been
known to live as long as 23 years in captivity (Haskins and Haskins
1992) although they are likely to be more short-lived in nature. In
some species, established colonies will produce or accept new queens
if the existing queen dies. Other species add additional queens as
the colony grows. In these species, nests can potentially last indefinitely
as new queens replace older queens, thus ensuring the constant production
of new workers. Individual workers generally live a few years but
detailed studies are few. Males can remain in nests for some months
and in some species they will over winter. However, most will die
within a few days of leaving their nests.