Life history and habits

Ants in New Zealand, like all ants, are social insects that undergo complete metamorphosis (egg, larvae, pupa, adult) and live in structured colonies with specialized castes (queens, workers, males). New Zealand has a small number of native species (11), but a larger number of introduced species (around 28) which are the most common pests. 
Life History
The general life cycle of an ant involves four distinct stages:

• Egg: The queen lays eggs. Fertilised eggs become females (workers or future queens), while unfertilised eggs become males.
• Larva: Eggs hatch into white, grub-like larvae that are immobile and fed by the worker ants.
• Pupa: After several moults, the larvae pupate. They resemble adults but are often encased in a silk cocoon (species dependent).
• Adult: The adult ant emerges, ready to perform its role within the colony. 

The entire process from egg to adult usually takes 6 to 10 weeks, depending on the species, temperature, and food availability. 
Caste System:

• Queens: Fertile females whose primary role is reproduction; they can live for up to 15-30 years.
• Workers: Sterile females that perform all the labour, including foraging, caring for the young, building the nest, and defending the colony. They typically live for 1-3 years.
• Males: Winged and their only function is to mate with the queen. They die shortly after mating, usually within a few weeks. 

Habits in New Zealand
Ants in New Zealand exhibit a range of habits and preferences, largely depending on whether they are native or introduced species. 
Native Species
New Zealand's native ant fauna is relatively sparse and less aggressive than species found in many other parts of the world. 

• Habitat: Most native species are found in forested habitats, soil, leaf litter, and rotting logs.
• Behaviour: They are generally less likely to invade human dwellings. The most common native, the southern ant (Monomorium antarcticum), is a generalist scavenger that also gathers seeds, foraging haphazardly. Other species like the large Pachycondyla ants possess a strong sting but are not typically aggressive toward humans. 

Introduced (Pest) Species
The approximately 28 introduced species are the main cause of concern, particularly the invasive ones that thrive in warmer urban environments. 

• Habitat: They often nest in wall voids, under paving stones, in house plants, and other protected areas near human activity.
• Behaviour: They are a nuisance around the house, attracted to food scraps and pet food.
  • Argentine ants (Linepithema humile) form vast "super-colonies" with multiple queens and are highly aggressive, displacing native species. They prefer sweet foods but are general scavengers.
  • Black house ants (Ochetellus glaber) are common in kitchens and bathrooms, attracted to sweets, and nest in wall cavities and fences.
  • Pharaoh ants (Monomorium pharaonis) are a major concern in commercial buildings and hospitals as they can potentially spread diseases like salmonella.
• Foraging and Communication: Workers use pheromone trails to guide others to food sources, although some species forage more haphazardly.
• Defence: Some species can sting, while others bite and spray formic acid for defence.