Agriculture Reference
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can exist among species in the degree of
polydomy. In one extreme, polydomous
colonies may occupy a few nests separated
by small distances among which worker
and resource exchange occurs frequently
(e.g. pavement ants, cornfi eld ants and thief
ants). Such colonies may be effectively
controlled with proper inspection and
through treatment using either baits or
sprays. In other species, the number of nests
and the area occupied can be substantially
higher (e.g. odorous house ants, ghost ants
and red imported fi re ants) making complete
eradication challenging, unrealistic and
often unnecessary.
In supercolonial ants, nest density is
extremely high and the nests extend over
distances large enough that worker exchange
among nests is virtually impossible.
Supercolonial species, however, still show
territorial behaviour at the scale of the
population and different supercolonies are
mutually aggressive where they come into
contact. Argentine ants and yellow crazy
ants are good examples of supercolonial
ants. The management of supercolonial ants
is obviously complicated owing to the
extremely high number of nests dispersed
over a large area. This diffi culty is especially
evident in large supercolonies that are
typically assumed to operate as a single
cooperative unit where food, workers and
brood are freely exchanged among all nests.
Recent work demonstrates, however, that
large supercolonies are discontinuous with
regard to resource fl ow and interactions
among nests are spatially restricted
(Buczkowski and Bennett, 2008; Heller
et
al
.,
2008). Complete eradication of super-
colonies is typically very diffi cult to
achieve, even on a regional scale, and sup-
pression, rather than eradication, is often
the goal. Finally, unicolonial species are the
most extreme example of polydomy where
the entire population comprises one huge,
widely dispersed colony that may stretch
for hundreds of miles. Introduced popu-
lations of Argentine ants often display this
colony structure.
When designing a management pro-
gramme for urban pest ants it is important
to remember that the majority of urban pest
ants are highly polydomous. Polydomous
colonies are organized into complex and
constantly changing networks of nests and
trails and numerous factors may affect the
extent of polydomy and consequently the
effi cacy of ant management. Monodomous
colonies may become polydomous in
response to various environmental factors
such as the discovery of attractive nesting
and/or feeding locations (Buczkowski and
Bennett, 2006) or simply outgrowing the
original nest (Levings and Traniello, 1981).
Likewise, polydomous colonies may revert
to monodomy because of the destruction of
alternative nesting sites or the exhaustion of
local food sources. Other factors such as
irrigation, mowing, periodic debris removal
and insecticide treatments may also affect
the distribution of nests. Many ant species
frequently move nests depending on the
environmental conditions. The ants
incubate the brood in exposed areas during
periods of optimal conditions (high
insolation) but relocate nests to more
protected areas as conditions deteriorate;
for example, when the nesting substrate
becomes too dry or too wet. Some species,
such as Argentine ants and odorous house
ants, may be seasonally polydomous
whereby the colony undergoes an annual
fi ssion-fusion cycle depending on ambient
temperature and the seasonal availability of
food (Heller and Gordon, 2006; Buczkowski
and Bennett, 2008).
The extent of polydomy and the spatial
arrangement of nests and trails have a
signifi cant effect on the effi cacy of pest
management efforts and should be taken
into consideration when designing ant
management programmes. For example, if
baits are used it is important to match the
number and distribution of baits stations to
the number and distribution of nests to
ensure that the toxicant reaches all nests.
Baits are a popular method to control pest
ants; however, baits frequently fail to
eradicate colonies and resurgences are
common. To obtain better results with toxic
baits, a thorough inspection focused on the
location of major foraging trails and main
nesting sites is key. Previous research on
odorous house ants, a major urban nuisance
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