African big-headed ants (Pheidole megacephala) have been in Australia for more than 100 years and are well established throughout many urban areas on the mainland, as well as on many islands.
They are listed as one of the 100 worst pests in the world. The ants are a major threat to biodiversity and ecosystems because they can readily out-compete and displace native invertebrates, especially ants. Rainforest ecosystems are most at risk.
The African big-headed ant tends to be a sap-sucking insect, making it a pest in many agricultural areas throughout the world. The workers can also damage fruit and plant roots directly. African big-headed ants can be a serious pest in buildings, forming large colonies where food scraps are available. They can also cause damage to electrical items such as power points.
What do they look like?
The major (soldier) workers have huge heads, contributing almost half of the body size. The minor workers, which are seen more often, are small (about 2 mm) and vary in colour from light to dark brown. African big-headed ants are slow moving, do not bite or sting, and have no smell when crushed.
Where are they found?
African big-headed ants are commonly found within and around infrastructure, and within any natural environment that they have been taken to accidentally by people. The ant can nest anywhere, especially in lawns, tree cracks, crevices in paving or concrete, hollow logs and pot plants. Nests are easily noticed as they actively mound soil, especially along concrete edges.