Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Invasive ants

Over 160 ant species have established outside their native range (see McGlynn 1999 for a recent list although many in his list for Hawaii are quarantine interceptions only).These include “tramp” species that have been spread throughout the world by human transportation and are often pests in urban environments.

Among the tramp species are several with the potential to invade native habitat in a new country and have an impact on the native fauna (e.g., Porter & Savignano 1990; Human & Gordon 1997; Hoffmann 1998). This last group we particularly do not want in New Zealand and we need management strategies to minimise the detrimental impacts of those already here.

Some of the worst global ant pests

The species listed below are some of the worst ant pests. New Zealand may not be climatically suitable for some tropical species.

Species Nests found in New Zealand Established in New Zealand
Anoplolepis gracilipes
Yellow crazy ant
yes no
Linepithema humile
Argentine ant
yes yes
Paratrechina longicornis
Crazy ant
yes no?
Pheidole megacephala
Big headed ant
yes yes
Solenopsis geminata
Tropical fire ant
no? no
Solenopsis invicta
Red imported fire ant
yes no
Wasmannia auropuntata
Little fire ant
no? no

Assessing the threat to New Zealand

A risk assessment scorecard was developed to quantify the threat to New Zealand of a range of ant species. 75 taxa were scored and grouped as high, medium, or low threats. A summary was prepared for each taxa, outlining why it was considered for assessment, and any mitigating factors that might reduce the risk of the taxa establishing in New Zealand (e.g., not climatically suitable) (Risk Summary pdf icon 559 KB).

Information sheets were prepared for all taxa scored as medium- or high-risk threats to New Zealand.

NB. The red imported fire ant (Solenopsis invicta) is considered to be the worst ant pest in the world. It has the potential to become a significant environmental, economic and human health hazard should it ever become established here. However, Solenopsis invicta was specifically excluded from consideration in this risk assessment as this species has already been subject to detailed consideration by Biosecurity New Zealand (Download report pdf icon1.2 MB).


  • Ward DF, Stanley MC 2013. Site occupancy and detection probability of Argentine ant populations. Journal of Applied Entomology 137(3): 197–203.
  • Stanley MC, Ward DF 2010. [Abstract] Do Argentine ants have impacts on ecosystems? Proceedings: Biodiversity : 2010 and beyond : programme and abstracts, University of Otago, Dunedin, 22-25 November 2010. Pp. 116-117.
  • Ward DF, Green C, Harris RJ, Hartley S, Lester PJ, Stanley MC, Suckling DM, Toft RJ 2010. Twenty years of Argentine ants in New Zealand : past research and future priorities for applied management. New Zealand entomologist 33: 68-78.
  • Ward DF 2009. The diversity, community composition and seasonality of native and introduced ants (Hymenoptera: Formicidae) in northern New Zealand. Myrmecological news 12: 195-200.
  • Stanley M, Ward D, Harris R, Arnold G, Toft R, Rees J 2008. Optimizing pitfall sampling for the detection of argentine ants, Linepithema humile (Hymenoptera : Formicidae). Sociobiology 51(2): 461-472.
  • Ward D 2008. Ecological partitioning and invasive ants (Hymenoptera : Formicidae) in a tropical rain forest ant community from Fiji. Pacific Science 62(4): 473-482.
  • Ward DF, Stanley MC, Toft RJ, Forgie SA, Harris RJ 2008. Assessing the risk of invasive ants: a simple and flexible scorecard approach. Insectes Sociaux 55(4): 360-363.
  • Fowler SV, Harman HM, Norris R, Ward D 2006. Biological control agents: can they tell us anything about the establishment of unwanted alien species? In: Allen RB, Lee WG ed. Biological invasions in New Zealand. 186 ed. Ecological Studies. 10. Berlin, Springer. Pp. 155-177.
  • Ward DF, Wetterer JK 2006. Checklist of the ants of Fiji (Hymenoptera: Formicidae). Bishop museum occasional papers 85: 23-47.
  • Ward DF, Harris RJ 2005. Invasibility of native habitats by Argentine ants, Linepithema humile, in New Zealand. New Zealand Journal of Ecology 29(2): 215-219.
  • Ward DF, Harris RJ, Stanley MC 2005. Human-mediated range expansion of Argentine ants Linepithema humile (Hymenoptera : Formicidae) in New Zealand. Sociobiology 45(2): 401-407.
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