African big-headed ant or Coastal brown ant(Pheidole megacephala)

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 ants will move significant amounts of dirt to make their nests – their activity around pavers becomes particularly obvious.
• Workers will travel significant differences between nest sites and to and front food sources.
• They sometime build shelter tubes for foraging trails, which can look superficially similar to termite mud tubes.

The big-headed ant only has a mild sting which is not painful to humans and its bite is not painful.

• Regular treatments (at least once a year) will likely be required to keep numbers down
• Following good hygiene practices, especially clearing away food and not leaving pet food out, will help minimise any foraging inside buildings.

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.