Coastal brown ant
The big-headed ant / coastal brown ant is one of the worlds worst invasive ants.
The big-headed ant is found worldwide in many tropical and sub-tropical areas. In Australia, it is common along the east coast, Perth and Darwin, but is probably more widespread.
It prefers moist, disturbed habitats – areas around human population are ideal. Typically, it nests outdoors in soil and under rocks / pavers. Sometimes it will nest indoors in wall cavities and plug sockets.
A multi-queen, multi-nest species. The colonies can develop into massive super-colonies completely dominating an area. They are a highly destructive invasive species and will out-complete most other ant species.
Colour: Mid brown / red
Size: 1.5 – 4.5 mm
Nodes on petiole: 2
There are minor and major workers, with the major workers (“soldiers”) having enlarged heads, from which they get their name. The major workers form around 1% of the foraging force, so may not always be visible.
Alates are not often seen as the colony expands through budding, whereby one or more queens with a number of workers move to set up another nest in a new location.
Although big-headed ants are often seen tending sap feeding insects, they show a strong preference for protein and lipid foods. They will typically feed on live and dead invertebrates, but will eat any dead animal material.
The big-headed ant only has a mild sting which is not painful to humans and its bite is not painful.
There are a number of other small brown ants, but the presence of major workers and sheer extent of infestations normally make identification straight forward.
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