FAQs related to Aristea
Argentine ants nest mainly in soil, retaining walls, and rock-gardens, under paths or cobblestones or at the base of plants in the warmer months. Wheelie bins and re-cycling containers, planter pots, cars and trucks also provide great nesting sites.
Some of the largest colonies have been found under the fake grass of tennis courts and around swimming pools.
Argentine ants are most active in dry, warm weather, but the onset of wet weather and cooler temperatures drives them into buildings.
Over-wintering nests can contain hundreds of thousands of ants, and can usually be found inside the north or east facing warmer walls and in ceiling cavities.
The small satellite colonies established during the summer months can come together into huge colonies during the winter months, only to expand again into dispersed nests when the conditions become favourable.
Argentine ant workers are small (2-3mm) and a uniform honey-brown colour (most other common household ants in New Zealand are black).
Their size and colour is similar to some of our native ants. However, unlike native ants, Argentine ants will be found both inside and outside a house.
Unlike many household ants, Argentine ants prefer protein foods like meat in summer, when they are breeding (although they also enjoy sweet things like sugar or honey).
These ants move steadily in defined continuous trails that can often be seen climbing up trees or plants, especially if they are flowering. Native ant species don’t do this.
In places, these trails may be five or more ants wide. If you lay your hand across the trail, Argentine ants will frequently continue straight over and even investigate further up your arm. Most other ants would greet this blockage with confusion, taking some time to re-establish their pheromone trail-markers.
Argentine ants look similar to another pest species - Darwin’s ants – but can be distinguished from these by the ‘squash and sniff’ test. When squashed between the fingers, Darwin’s ants have a distinctive, formic odour; Argentine ants do not. Women are generally better at picking this smell than men.
Other ants commonly found around homes:
- White footed ants- Very common. Will eat most things but very attracted to sugar. They are shiny, give off a pungent odour when disturbed and form large nests in walls and ceilings of structures.
- Bigheaded ants- Red /brown, with two sizes of worker. The heads of major ants are noticeably large. They feed on cat food, dead insects and other protein sources.
- Black house ant- Very common, but only about half the size of the white-footed ant. Eats mainly sweet foods and builds large nests.
- Forceps ant- Large and run around erratically; they look like they don’t know where they are going. They feed on animal food and are usually found in concrete paths, curbs or cobble-stones. They will bite and are a problem around BBQs and swimming pools.
- Darwin’s ant- Smaller than argentine ant (less than 2mm), but give off greasy odour when squashed. They have many of the same behavioural characteristics .i.e., soil nesting species, huge populations.
For more details on Argentine ant Identification visit:
http://www.landcareresearch.co.nz/research/biosecurity/stowaways/Ants/AAidentification.asp 
Anything transported from point A to point B can potentially harbour Argentine ant nests.
Materials that are most at risk of harbouring a nest include rubbish, and garden or nursery products like potted plants, garden mulch, bark chips, and compost.
However, these ants also readily establish nests in cars, caravans, or even aircraft. And in this way can spread themselves across town, or around the country with ease.
Argentine ant infestations are frequently not detected until they have reached the stage of becoming a human nuisance. This may take two years or more. By the time they are detected, the ants are probably well established and may even have spawned sub-colonies that have hitched a lift elsewhere.
Argentine ants invade and colonise an area in two ways: budding and jump dispersal.
Budding
Unlike many other ants, Argentine ant queens do not go on nuptial flights, and so form new nests within ant-walking distance of the old nest. After mating, a young queen will simply walk away with some workers, and establish a new nest nearby. Left to themselves, colonies would increase by little more than 200 meters/year.
Jump dispersal
However, young queens will readily ‘bud off’ with a few workers and establish their nests in nearby vehicles, planter pots or wheelie bins. This done, they could end up anywhere.
This ability to ‘hitch’ a lift with humans makes the Argentine ant so challenging to control. And as these ants produce around ten times more queens than other species, the challenge is magnified.
Human-mediated dispersal within suburbs across a city, and between neighbouring towns is essentially creating a large number of small ant populations throughout New Zealand, and these are likely to act as centres for further expansion.
The Argentine ant has a wide dietary range and produces large numbers of aggressive and industrious workers.
They are one of a few ants species worldwide that have been identified as capable of invading native ecosystems and displacing native species, and because of this are listed as one of 100 of the world's worst invasive species by the Global Invasive Species Group, IUCN
Argentine ants are omnivorous, with neighbouring colonies being genetically related. The relative lack of in-fighting between colonies makes the species highly competitive in the ant world.
When a colony has fully infiltrated an area, resulting in its complete dominance over other arthropod species, it has achieved ‘Super Colony’ status. The lack of other ant species and insects in the surrounding area is a clear indicator of this.
Super Colonies allow Argentine ants to form extensive, interconnected networks, not only through the suburbs of a town but even across vast distances.
In Mediterranean Europe, where Argentine ants have been established for many years, recent studies indicate the existence of a single, vast colony, stretching almost six thousand kilometres from Italy, through France, Spain and around the corner to Portugal.
New Zealand is particularly prone to the ecological impacts of exotic ants because our native flora and fauna has evolved without a large and ecologically dominant ant fauna.
Impacts on horticulture
Argentine ants can severely affect commercial horticulture by their tendency to nest in tree roots and by their farming and protecting honey dew producing insects (eg. aphids and scale insects). They hinder the growth of plants and trees and/or damage crops, and adversely affect pollination.
Pip fruit, stone fruit, subtropical fruit and cut flower crops are at medium risk; while olives, nuts, kiwi fruit and berry fruit are identified as medium-low risk crops.
New Zealand exports fruit to most countries, and these ants could affect our ability to comply with export requirements. The Argentine ant is not present in a number of Asian countries - for example China and Korea - and exporting goods contaminated with the ant to these countries could be detrimental to New Zealand’s trade image.
As these ants actively protect and tend sap-sucking insects, this could cause serious difficulties for organic growers who rely on biological control of their plant pests.
Lester, P.J.; Longson, C.G. 2002: Argentine ant distribution investigation: Horticultural areas. 
(7401 KB) Unpublished Victoria University of Wellington contract report for MAF Biosecurity Authority.
Impacts on biodiversity and ecosystems
The impacts of Argentine ants on both native invertebrates and vertebrates are well documented in Hawaii and California.
A recent study around Auckland has shown that open canopy habitats are most at risk of invasion, while forests are probably less susceptible.
Based on this, researchers suggest open habitats and relatively open scrub environments – including coastal conservation areas - in northern New Zealand are likely to be vulnerable to invasion by Argentine ants.
However they suggest that Argentine ants will not invade the interior of intact, closed-canopy indigenous forest.
“Harris, R. et al. 2002: A survey of the current distribution of Argentine ants, Linepithema humile, in native habitats in New Zealand, and assessment of future risk of establishment. Landcare Research Contract Report: LC0102/105 for MAF Biosecurity Authority.
Urban impacts
The Argentine ant has already become a significant pest in some New Zealand urban areas, persistently invading homes and commercial buildings in large numbers.
Overseas, in heavily infested areas residents are unable to live, relax or work comfortably inside or outside the home. On windy days the ants are blown off tree leaves onto people and their food. They constantly nip at exposed feet and legs in the garden and in the house, and trail into beds at night, disrupting sleep. Some people react to their bite.
Extreme measures have had to be taken by residents to prevent the ants entering bedrooms and beds, for example placing bed legs in pots of water; moving beds well away from walls and curtains, and ensuring sheets and blankets are tucked up off the floor.
Residents in affected areas report a notable absence of most of the common garden insects following the establishment of the ants. They have also noticed reduced cropping of beans, peas and other home-grown vegetables.
On the other hand, affected residents find themselves fighting to control increased aphid and scale populations on citrus and ornamental shrubs (due to the ants nurturing these creatures), with some trees succumbing to the resulting stress and disease.
For more details on Argentine ant impacts visit the Landcare Research website or read Potential impacts of the Argentine Ant (Linepithema humile) in New Zealand and options for its control.
Argentine ants were first detected as an established population in Auckland in1990. They have since spread quickly and are now present in many North Island cities and in two South Island locations.
http://www.landcareresearch.co.nz/research/biosecurity/stowaways/Ants/AAdistribution.asp
Argentine ants are often found closely associated with humans and human activities - e.g., in houses, gardens, plant nurseries and industrial areas. A recent study [WARD, ET AL .PDF] found human-mediated dispersal is primarily responsible for the spread of Argentine ants in New Zealand.
These ants hitch a ride in vehicles (including aircraft) and on transported materials of all kinds. They have the potential to spread throughout much of the North Island and northern South Island, as well as some South Island cities.
http://www.landcareresearch.co.nz/research/biosecurity/stowaways/Ants/AAfuturedistribution.asp
A single male Asian Tiger Mosquito was trapped at Shed 8 on the wharf at the Ports of Auckland on Friday 1st March 2007 as part of a routine mosquito surveillance program. Investigations are currently underway to establish whether this is a one off event or whether it is part of a localised population.
The Asian Tiger Mosquito (Aedes albopictus) occurs throughout the tropics of Southeast Asia, the Northern Pacific and Indian Ocean Islands, north through China and Japan and west to Madagascar. The Mosquito has also spread to North and South America, with more recent introductions into areas within Africa, Australia, the South Pacific Islands and Europe.
Mosquitoes go through four separate and distinct stages during their life cycle: eggs, larvae, pupae (resting stage), and adults. They have an elongated proboscis (mouth piece) with which the female bites and feeds on blood.
Our mosquito identification experts use microscopes to identify physical differences to tell different species apart.
Adult Asian Tiger Mosquitoes range in size of approximately 2 mm to 10 mm and have black bodies with a conspicuous pattern of white stripes. There is a distinctive single white band (stripe) down the length of the back. There is also a native New Zealand mosquito that has white stripes, so the best indication of an Asian Tiger mosquito may be aggressive daytime biting. Adult female Asian Tiger Mosquitoes feed on humans, animals, birds and frogs.
MAF Biosecurity New Zealand is encouraging members of the public in the Ports of Auckland/downtown Auckland area to report unusual mosquito activity. Unusual activity means aggressive daytime biting, usually in shaded outdoor areas. If possible collect a sample by placing it in a sealed container and report your find to the Ministry of Health’s hotline 0800 MOZZIE (0800 669943).
If you are concerned about mosquitoes you can avoid being bitten when outdoors by wearing a repellent cream or spray preferably containing DEET (diethyl toluamide) and wearing light-coloured protective clothing such as long sleeved shirts, long pants and hats to minimise skin exposure.
Exotic mosquitoes are most likely to enter New Zealand by way of:
- being lodged in deck cargo on international ships
- breeding in water storage and open containers on fishing boats and yachts
- breeding or attached to used tyres
- breeding in cavities and containers on used vehicles, used machinery and other imported goods.
The Ministry of Health and the Ministry of Agriculture and Forestry (MAF) are working together with Auckland Regional Public Health Service, the Ports of Auckland, and the Auckland City Council to determine if an Asian Tiger Mosquito population is present.
An enhanced surveillance programme is currently seeking to identify, and if necessary contain, control and eliminate any Asian Tiger Mosquitoes found in the area before they can spread further. This programme includes the placement of additional traps and the identification and elimination or treatment of all potential habitats in the port area.
The Asian Tiger Mosquito is defined as an 'unwanted organism' under the Biosecurity Act 1993. This is because it would be able to breed in New Zealand and could spread some very serious human diseases. These include Dengue fever, Eastern equine encephalitis virus, Japanese encephalitis virus, LaCrosse encephalitis virus, Ross River virus, St Louis encephalitis virus, Western equine encephalitis virus, West Nile virus, and Yellow Fever.
Only one male specimen (males do not transmit viruses) has been found so far, and based on the information obtained to date we believe the risk of contracting one of these diseases through this route is extremely low.
If it became established in New Zealand, it has the potential to spread throughout many areas in the Northland and Auckland regions depending on rainfall and temperature variables. Other North Island regions (e.g. Hawkes Bay) may also be suitable for establishment.
The Asian Tiger Mosquito prefers rural and vegetated habitats. However it can also successfully breed in urban environments. It breeds in natural and artificial containers, and in fresh to polluted and even brackish water.
For more information on human influenza and up-to-date NZ pandemic information, visit www.moh.govt.nz/pandemicinfluenza .
For international information visit the World Health Organisation at www.who.int/csr/don .
For information on countries where birds are affected, you can visit the OIE website at www.oie.int/downld/AVIAN%20INFLUENZA/A_AI-Asia.htm .
The risk of bird flu entering New Zealand in migratory birds is considered very low but good biosecurity practices are crucial in minimising the likelihood of entry of any type of avian influenza virus.
The main symptoms to look for in poultry are:
- Sudden and unexpected deaths
- Rapid spread of disease throughout the flock
- Depression and loss of appetite
- A drop in egg production
- Nervous signs such as unusual head or neck posture, convulsions
- Swelling and blue combs and wattles
- Coughing, sneezing and diarrhoea
In the event of an outbreak of avian influenza in New Zealand MAF would activate its Technical Response Policies and Operational Plans.
All highly pathogenic avian influenza viruses will be stamped out. As with other animal disease responses, independent technical advice will be sought and a number of response options evaluated to decide the best response option.
In addition to enhanced biosecurity in collaboration with poultry owners, response options include:
- Quarantine
- Culling
- Planned slaughter as part of normal management
- Movement control of risk goods
- Tracing and local surveillance to locate the source of infection and determine the extent of spread
- Decontamination
World Organization for Animal Health (OIE) reporting requirements for avian influenza and New Zealand's commitment as part of a global network for the early detection and warning of highly pathogenic notifiable avian influenza (HPNAI) infection means that stringent surveillance is needed.
New Zealand has been undertaking surveillance in wild birds, including migratory shorebirds & waders, local waterfowl and other species, since 1976. Testing of migratory birds has increased since the outbreaks in Asia and a comprehensive programme of surveillance in commercial chickens (turkeys, game birds, farmed ducks and geese) is ongoing.
These programmes provide the evidence needed to demonstrate to the OIE New Zealand’s freedom from highly pathogenic notifiable avian influenza.
For a summary report detailing New Zealand’s Avian Influenza Surveillance Programme see: http://www.biosecurity.govt.nz/files/biosec/pubs-media/pubs/surveillance/issue-34-2/surveillance-34-2.pdf (553 KB)
New Zealand is well prepared to respond to an outbreak of avian influenza. MAF has comprehensive response plans and policies for highly pathogenic avian influenza or any H5 and H7 subtypes of avian influenza as well as any other exotic strains of avian influenza of regulatory concern.
As a member of the World Organisation for Animal Health (OIE), New Zealand is expected to conduct surveillance to demonstrate our freedom from highly pathogenic notifiable avian influenza (HPNAI).
Highly pathogenic notifiable avian influenza and all H5 or H7 subtypes of avian influenza virus are classed under the Biosecurity Act as a notifiable exotic disease in New Zealand. This means that any suspect case must be notified to MAF immediately.
Yes. New Zealand imports live chicken and turkey eggs from the United States, Canada, the United Kingdom and Australia. The eggs are hatched and the chicks reared in strict quarantine conditions under veterinary supervision, according to New Zealand import health standards. Strict biosecurity measures, stringent testing regimes for avian influenza and other exotic diseases and New Zealand's major poultry disease free status proves that this system is highly effective.
The New Zealand Food Safety Authority advises that avian influenza is not a risk in New Zealand in terms of food safety. Consumers can be confident that the raw poultry and table egg products purchased in New Zealand supermarkets are New Zealand produced and free from avian influenza.
There is no evidence that any of the human cases of avian influenza overseas occurred as a result of eating cooked poultry products. Human cases are generally a result of direct contact with live and infected birds or the consumption of raw poultry meat or blood.
There are some highly processed products which are imported including canned meat, chicken paste, powdered chicken stock, dried egg yolk and feathers. Any virus would have been killed during processing, posing no risk to either animal or human health.
No. There have been no imports of live birds to New Zealand since 1997, except for occasional zoo species such as flamingos.
MAF Biosecurity New Zealand Quarantine Officers inspect consignments of cargo, passengers, luggage and imported commodities using dogs and sophisticated X-ray equipment.
Potential routes of entry include illegal imports of poultry and unprocessed poultry products or the movement of contaminated fomites (virus in avian faecal material on packaging, clothing, equipment etc and other commodities from infected areas).
New Zealand prides itself on keeping disease at bay with strict biosecurity measures at the border and stringent testing regimes. Import Health Standards prevent entry in imported risk goods, and our unique major poultry disease-free status indicates that this system is highly effective.
Over 5000 samples have been taken from wild birds (migrating and resident species) in New Zealand since 1976. A small number of low pathogenic notifiable avian influenza viruses (H5 or H7 subtypes) have been found in healthy mallard ducks.
All influenza viruses are unstable and constantly changing. New human influenza viruses emerge every year.
Human pandemic viruses are very rare but occur when a new virus, to which humans have no immunity, emerges. Genetic studies have shown that some human pandemic influenza viruses have been derived from avian influenza viruses.
There is no evidence of H5N1 being readily transmitted from one person to another but recent information suggests this may have happened in a small number of cases where family members live in close proximity and/or have tended those that were ill.
Adaptation to, and evidence of, sustained spread between humans would indicate the emergence of a potential human influenza pandemic. To date, this has not happened.