Saturday, August 10, 2013

The Story of Ants – Biology and Behaviour, Implications for Control

I have recently been giving some talks on pests and diseases in the home and garden and how to solve problems.

I thought it might be useful to publish some of the notes from these talks. This first one is about ants. I have summarised the biology and behavior of ants and what the implications of these are on how to control infestations.





Nuptials
  • Flying ants (not all species) are ants mating
  • Queens and males mate in flight
  • After mating males die and queens fly to seek nest (not usually more than 100m from original nest)
  • Queen looses wings
  • Starts colony
Flying ants annoy people as there can be many thousands. Treatment is not usually effective and most of the ants will die within a day or two.

To prevent infestation it may be advisable to treat possible nest sites in area with spray (NO Bugs Super, NO Ants) and use granules (Ant Sand and Lawngard Prills).


Nest Site

  • Dry – rain could drown nest
  • Warm – insects are more active when warm
  • Sunny – radiant heat can make ground and ants warm even on days with cool air temp – micro-climate
  • Sandy soil – easy to dig out nest chambers, well draining
  • E.g. under concrete path, under rock etc.
  • Sometimes nest in building, but if so, it probably be in exterior wall or eaves on sunny side
Deny ants nest sites: Repair cracks in concrete, paths, walls, etc. Apply Ant Sand to cracks and edges of paths. Apply Lawngard Prills to soil areas (particularly flowerbeds and lawns close to house) water in.

Stop ants getting in; spray base of walls, doorways, windows and around vents, where pipes/cables etc. run through walls.


Building Colony

  • Queen lays eggs which hatch as sister workers (no males)
  • In early stages queen will forage for food
  • Then workers take over gathering food and queen just lays eggs
  • Workers tend eggs and maintain nest
  • Colony grows where there is food, nest site, warmth, low competition
Early control, when numbers are low, is easiest.

Budding

  • New queen/s produced in nest
  • New queen and a few workers start new nest
  • New nest genetically similar or the same as old nest – co-operation – same colony – super colony
  • NZ imported species spread from one or few original colonies – all genetically similar and will co-operate – may be one huge colony (super colony)
Important not to disturb nest (particularly one with multiple queens) as disturbance causes queens and workers to bud; heading off in different directions to set up new nests; he result being spread of the problem. I.e. do not spray nest site before baiting for ~2 weeks first. When spraying or using granules at nest site treat around nest entrance/s not in nest entrances.

It is likely that other nests are in the vicinity. Controlling/killing one nest is rarely enough to get rid of them permanently. Ants are likely to spread in again from a neighbouring nest/colony.


Multi-queen colonies/nests

  • Some species will have more than 1 queen in a nest (e.g. Argentine Ants, Darwin Ants)
  • Faster growth of numbers
  • Easily spread
  • Argentine ant queens forage
  • Very easily spread on cars, plant pots
  • 1 queen and 20 workers enough to found new nest/colony
If you have ants (particularly Argentine ants) spray plant pots, boxes, car undersides etc. before moving to other properties.

Numbers – Nest and colony

  • Thousands, tens of thousands, even hundreds of thousands in single nest
  • Super colony – many millions?
  • ~5-10% foraging workers – so what are seen is small part of colony
Killing all the workers (foragers) that are seen in a garden or house will not kill the colony. Nest can reproduce and replace 5-10% in a few days. Baits are most effective as the poison is taken back to the nest to kill at/in the nest. Use sprays and granules as barriers to nuisance trails.

Feeding

  • Protein – insects, seeds…..
  • Needed for colony growth and producing larvae
  • Some species target other insects and invertebrates that compete with them for food; removing competition (Argentine ants when moving into new area, biodiversity threat)
Kiwicare Gel Bait contains liver protein.
  • Carbohydrate – sugars, plant material (fungal breakdown)…. 
  • Energy; needed when ants/nest very active
Gel and liquid baits contain sugars.
  • Farming
  • Some ants feed on honeydew (sugary fluid) excreted by sap sucking insects such as aphids, scale insects, mealy bugs.
  • Ants protect sap suckers from attack by predators in a mutualistic (benefits both) relationship
Control aphids, scale, mealy bugs on garden plants with Super Spectrum, Carbaryl etc. so that ants cannot feed from them.

  • Very little fats or oils – ‘healthy lifestyle?’
  • Scouts sent out from nest to search for food – pheromones in nest ‘tell’ scout what sort of food the nest needs; protein or carbohydrate
  • Find food and lay pheromone/chemical trail back to nest
  • Tells (by pheromone and behaviour) foraging workers to follow trail to food
  • Foraging workers follow trail like ‘robots’ and may walk past and ignore other food
  • Each time a forager returns with food it also adds to chemical trail, encouraging more workers to follow it to food
  • As food runs out trail diminishes and fewer workers follow it until it stops
  • Ants live in a ‘chemical world’ and can be attracted to or repelled by some chemicals including cleaners, insecticides etc.
Baits must be placed on clean places with no deterrent chemicals. Do not spray areas around baits. Use sprays as barriers.

Baits may be ignored for days when ants are feeding somewhere else or the colony needs a different food type. Do not move baits, even if they are not being fed on. But replace bait as it is eaten and if it gets dried hard.

  • Collected food fed to other workers, queens and larvae in nest that do not go foraging
  • Direct feeding – food carried by foragers and passed straight on to others
  • Regurgitation – food ingested and regurgitated to others
  • Anal secretion – food digested and honeydew like secretion for rear fed to others
  • Sterile eggs – food digested and sterile egg produced which is fed to others e.g. White Footed ant
  • Farming – food (plant and insects) infected with fungus – ants feed on fungus
For some ants (e.g. white footed ant) bait toxins are not easily passed on to others in a colony as the ant has ingested the poison and died, or the toxin is filtered out of production of anal secretion or sterile eggs.


Species

  • Almost all species that are pests have come in from overseas (invasive).
Argentine ants – world’s worst invasive.
  • No smell when squashed
  • Trails like motorway; several ants wide
  • Small (2-3mm) brown to black (like Darwin and White footed)
  • Super colonies
Darwin ants
  • Smell when squashed
  • Trails single file
  • Small (2-3mm) brown to black (like Argentine and White footed)
  • Super colonies
White footed ants
  • Smell when squashed
  • Small (2-3mm) brown to black (like Darwin and Argentine) 
  • with lens it is possible to see pale ends of legs (feet)
  • Super colonies
Black house ants
  • Small (2-3mm) black
  • North island
  • Native garden ant
  • Larger (3-5mm) than above
  • Black
  • Smaller numbers in nests
Biosecurity Risk Ants – Not yet established in NZ



Identification of ant species can be important in knowing how to treat most effectively.


Colony Death


  • No queens – in super colony species a queen can be recruited from another nest
  • No food
  • Nest drowned out
  • Cold
A combination of control methods is almost always required to get rid of an ant infestation. Pro-active control each year is the best method.

Ants outside in the garden are rarely a problem, only when they trail indoors do they become a pest. Therefore, treat to keep ants outside and prevent their entry.


What is the world's largest ant? The Eleph ant.

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