Darwin’s Ants are light to dark honey-brown, and 2 millimetres long. They are similar in appearance to Argentine Ants but give off a strong odour when crushed; there is little or no odour for Argentine Ants, to whom they are closely related. Darwin’s Ants are native to Australia and were first recorded in Christchurch in the 1970s. They are now found widely scattered through the northern and eastern parts of the North Island and in the upper South Island. Darwin’s Ants in New Zealand form extremely large colonies and behave similarly to Argentine Ants.
Reasons for the Strategy
Darwin’s Ants are easily spread by human-related activities (eg, movement of pot plants, vehicles, etc). They are not capable of stinging but will enter houses in large numbers foraging for sweet foods. They are a major pest for householders in areas where they are established. They can reach large densities in urban gardens, becoming a nuisance and may displace other invertebrates. Darwin’s Ants tend aphids and mealy bugs and may also spread disease in the same manner as Argentine Ants. There are numerous potential impacts of Darwin’s Ants on the commercial sector in urban environments; including ants invading food processing plants and becoming important pests of the hospitality industry. Darwin’s Ants have been found predominantly in urban areas and on the margins of native habitats. There is concern about their spread into coastal shrublands, especially in areas like Abel Tasman National Park. Their potential impact on native ecosystems in New Zealand remains largely unknown. The development and manufacture of an ant bait has made it possible for land occupiers to reduce ant numbers to very low levels, but eradication seems impossible to achieve in urban or industrial settings.
Darwin’s Ants are assessed at “3” on the infestation curve. Extensive areas of suitable habitat, and the potential for them to cause significant adverse effects, mean the benefits of containment control far outweigh the costs.
To address the adverse effects of Darwin’s Ants during the term of the Strategy by:
- Containing Darwin’s Ants in the infested urban areas.
- Keeping uninfested areas clear of Darwin’s Ants.
The alternative option of “do nothing” or relying on voluntary control will not achieve the objective of containing Darwin’s Ants, and will result in significant additional costs to the community with respect to lost production and natural values, and the increased cost of control in the future.
Strategy Rule for Darwin’s Ants
- The occupier of Darwin’s Ant-infested land shall bait to control Darwin’s Ants.
- The occupier shall take all reasonable precautions to prevent the spread of Darwin’s Ants in rubbish, pot plants, equipment and vehicles.
A breach of Strategy Rule 6.4.5 is an offence under Section 154(r) of the Biosecurity Act 1993.
Biosecurity Act Requirement
No person shall knowingly sell, propagate, breed, release, or commercially display Darwin’s Ants, under Sections 52 and 53 of the Act.