Fenua Animalia - Litte Fire Ant

The LFA

Biology

Wasmannia auropunctata, or Little Fire Ant (by analogy with the Great Fire Ant, the Red Imported Fire Ant) or LFA, wears a biology as stricking as sheming.

It is part of the 8 Ant species ranked as Super-invasive.
To joint this very closed club there is to own the following characteristics:

Unicoloniality: No agressiveness among adjoining nests
Adaptation to Environments disturbed by man
Omnivorous: Opportunists, flexibles
Polygyny: Several queens by nest, without hierarchy
Continuous foraging: 24 h / 24
Fast mobilization: Levy en masse on discovery of resource
Tendency to migrate: Common nest moves
Very strong agressivity
Easu demographical explosion

This one, in plus, owns a dreadful venom, which allows it, with the previous characteristics, to enter the Worst Pests Worldwide Top 10.

Individuals

It is a tiny ant (1.2 mm):

Marks are millimetres:	Distinguishing marks:

Queen and worker on a milimetre calibrated ruler. Photo: Tahiti 2004.	Photo: Tahiti 2006. See also: PaDIL-Wasmannia auropunctata

It is one of the ten Worst Invasive Species spread by man.
Its expansion is closely watched by the International Community, looking at the devastation it induces when it arrives and its population explodes.
An UNO commission has even been established to try to reduce the impacts of these pests: The Invasive Species Specialist Group, or ISSG. (see above)

Nests

We have sampled a nest to evaluate numbers. Here it is, in alcohol and spreaded in a Petri box (diameter: 10 cm):

This photo shows only ants: All crumbs and dust grains have been removed.
Gradations are in millimetres and the tiny brown-orange grains surrounding the black queens are shrivelled workers.
Here, we counted 80 sexed individuals. It is a sample only: Some may have escaped during catching.
Thus, a nest is able to shelter about a hundred of queens, each surrounded by workers, even more numerous.

The whole, put back in its flask, occupies a cubic centimetre only.

In the wild, its thickness may be extremely tiny: They settle commonly within banana tree trunks, between the strata of leaves!
(Note for non-tropical countries readers: A banana tree is shaped like a large leek: Leaves have no leafstalk, they are stuck together to form the trunk and separate further, above it. New leaves spring from its centre. They push the others aside to the periphery, rise vertically, then open and spread out: Oldest leaves, in periphery, make, at death, the "bark". In trunks, the free space between leaves is smaller than 1 mm, even so that is wide enough to shelter Little Fire Ants nests! )

A nest may, thus, accommodate anywhere:

in the ground, fissures, in an underground termits gallery after they have killed the occupants,
in a decaying branch, a coconut on the ground, a flower pot,
in trees,
between stacked or assembled planks or bricks, wooden cases, transport pallets,
in houses: walls, gutters, roofs, electric jackets and galleries,
in old abandoned cardboard boxes, dustbins, immobile linen, clothes, furniture,
in cars, vans and building machines, big and small boats, crates, containers,
in short, everywhere!

Emilie's case in Mahina is a clear example.

When disturbed, they move around the nest very easily. If broken in pieces, each carries on.

Whatever the number of queens and the number of nests in contact is, they behave like a single colony: They form a diffuse meta-organism able to reach gigantic proportions (several hundreds of kilometres in New-Caledonia and in Gabon).

Reproduction

In Mahina, by the frontier of the widest known colony, we have been able to count, on a cleared lawn, 5 nests per square meter.
An estimate of 10 nests per cube meter in arboreal highly contaminated areas is thus probably below the reality.

According to the ISSG scientists, a queen is able to hatch about 70 eggs a day.
This gives them a theoretical reproduction strength of 100 (queens) * 10 (nests) * 70 eggs/day in such places,
this is 70.000 more ants each day and by cubic meter.

Transferring these data to ground surface, we get: 70.000 * (100*100m) = 700.000.000 new ants each day per hectare.
In other words, when conditions are suitable,

they are, by hectare, increasing by 0.7 billion per day!

On Tahiti, the surface area of currently known colonies (end-2007) is estimated to be ... 600 hectares.

workers come to contact workers feel the queen workers stick the queen, or climb on it
Queens attracting workers: Few seconds separate these photos.
Mahina - Taharaa - dec. 2006

Biotopes

They like:

Areas disturbed by man: homes, sites, fields ;
Quiet places: shaded, sheltered from wind ;
Humidity: They need water(they float) ;
Plants with smooth leaves where they install their herds of scale insects and lice the secretions of which they feed upon ;
Fat and sweet fruits, flowers and buds, meat.

They dislike:

Direct sun, wind, arid lands: Asphalted roads are impassable deserts for them ;
Cold: There is no in England, but in some air-conditioned greenhouses and buildings where they have been accidentally brought, they do not survive. The same phenomenon is observed in some other non-tropical countries, like Canada ;
Other ants and other species competition: They expel them from their territory, or kill and eat them. They are responsible for multiple species extinction and are a serious threat to local Biodiversity.

There is no known natural predator for this species.

Under a stone: Queen, workers and eggs. under the same stone: Two queens, workers and eggs.
Polygynic nests (of several queens): Three different queens, token among others, on the same stone of less than 10 cm picked up along a road in Mahina.
Mahina - Taharaa - dec. 2006

Damages

It eradicates most of the living organisms from the territories it conquers.
Each individual may use its sting several times at a stretch.

Its venom is powerful: Each sting burns intensely for more than an hour.
They may induce blindness to any vertebrate, a phenomenon known as Florida Keratitis.

The most visible damage is, obviously, in the widest colony of Mahina.
They are numerous and cover a wide range, impacting in addition the Agriculture and Tourism industries, so not only:

Crops

Some vanilla fields are abandoned for several years.
All the beehives have disappeared:

Ants enter the beehive, kill queens and take eggs, bodies and honey.
Entry into small valleys is forbidden to persons not wearing an ant-proof overcoat:

Reminder: Each ant may sting several times and the effect of each sting lasts after more than an hour.
Gardens and playgrounds are deserted.
In some homes, trees have been cut, by those weary of being attacked by ants falling from leaves when passing under them:

Homes

Ants enter homes.

Inhabitants are, of course, deeply disturbed and they induce sometimes short-circuits in electrics when they invade the cladding:

When it invades homes, the situation becomes quickly unbearable. Emilie's case is a detailed example.

Pets

The Florida Keratitis syndrome resulting in blindness is common on Pets:

Stings to the eyes: Marinette in August 2005.
Corner: June 2002.

Stings to the eyes on Mahina Pets resulting in permanent damage.

There is >no known cure today for the Florida Keratitis.

Persons

allergic reactions occurs also:

Here, while cleaning weeds along a house wall:

attacks are unavoidable.

After 24 hours, with an allergic person, the effects are still visible:

No fatal case (Quinke's oedema) is recorded yet on Tahiti, for now, but they do occur.

Reminder: Each ant may sting several times and the effect of each sting lasts after more than an hour.