Source: TW
Intro
The Argentine ant global set of supercolonies is one of the largest cooperative societies on earth, it is also one of the most aggressive. World war ant has been raging for over a century, from Japan to South Africa.
Origin
But where did it all begin?
Argentine ants (Linepithema humile) are about 2.5mm in size, native to Argentina, and considered an opportunistic, flexible and aggressive species. Within their native range their genetic diversity is wide and different colonies regularly fight each other.
Supercolony formation
However, outside of Argentina their genetic diversity is extremely low, and often entire continent’s worth of Argentine ants can be traced back to a small number of individuals. Despite living in separate colonies these ants recognise one another as kin, and do not attack.
The result of this is that invasive colonies of Argentine ants form peaceful ‘supercolonies’, capable of dominating huge areas of land.
California
One of the largest we know of is called the Very Large Colony, stretching from San Diego to San Francisco, with maybe one trillion members.
This colony formed over a century ago, when ants were accidentally transported from Buenos Aires in the 1890’s to Louisana on steamboats and then California, likely by train.
External raid
Their internal cooperation and externally directed violence has made them unstoppable. They eat seeds, farm aphids for honeydew and destroy other ant’s nests for food.+++(5)+++ Seed-harvester ants have been known to plug up their entrances to prevent Argentine ants entering, but they will wait and starve them out, launching waves of assaults until they decimate the nest.
War
The Very Large Colony has one major rival supercolony - the Lake Hodges colony - which is separated by several freeways. In 2004 researchers realised that 30 million ants a year were being killed on the borders between the two colonies, ants fighting over the bodies of their dead.
The battlefields between the colonies can stretch for miles, places where ants wrestle with one another for unknown amounts of time, ripping off legs, antennaes, heaping up corpses and shifting backwards and forwards as territory is won or lost.
Spread out
California has been won by the Argentine ants, and the Very Large Colony control the port cities of Richmond, Oakland, San Francisco, Long Beach, Los Angeles, and San Diego. This is important because they have used the ports to spread across the world, exploiting the sea lanes.
We’ll look at this in the next thread - the global dominance of the Argentine ants by use of the global shipping system. We’ll also see how other ants are fighting back against this intrusion - welcome to world war ant!
Having examined the invasion and consolidation of the Argentine ant in California, in particular their control over the major port cities, we can now turn to their colonisation of the rest of the world through the exploitation of human-run shipping lanes.
New Zeland
In the previous thread we saw how the VLC (Very Large Colony) controlled access to the ports. One of their first presumed dispersals was to New Zealand, possibly in 1990. The rapid colonisation of the country has been mapped in some detail. Their impact cannot be overstated.
Aside from attacking honey bee hives, native ants and insects, baby birds and even humans, they also destroy ecosystems by recruiting aphids for their honeydew. It is possible that the Argentine ants will suffer colony collapse with increasing rainfall, but their flexibility and high novelty seeking behaviour leads some experts to conclude that they are “only at the beginning of their invasion of New Zealand”. Ominous!
Japan
Japan presents another story however. The Argentine ant invasion of Japan has not been a single dispersal, but a brutal multi colony affair, with three supercolonies (A,B and C) ruthlessly battling it out around the port of Kobe.
More worryingly, a new supercolony in Nara prefecture appears to have mastered using the river to increase their nest budding and dispersion mechanisms. Most likely through ‘rafting’, the Nara clan has rapidly consolidated control around the water’s edge.
The impact on Japanese ants has again been documented, unfavourably. Where Argentine ants come into contact with natives they seem to eradicate them quickly. Curiously two species were not destroyed though, one much smaller and weaker and one that lives in trees.+++(5)+++
South Europe
The southern European supercolony dwarfs almost all others, stretching over 6,000km of territory, with two smaller rival colonies (Catalan and Corsican). The scale of the main colony has led to human intervention, hoping to play off the supercolonies against one another.
A truly terrifying realisation has been to discover that the VLC in California and the main colonies in Japan, Europe, New Zealand, Australia and Hawaii, are all the same colony! They recognise one another and do not attack. The earth is spanned by one single, massive hypercolony.
World war
So far we’ve only focused on one species of ant and how it has spread around the world. But they have competitors, which is what makes this a true world war. The red fire ant (Solenopsis invicta) is the eternal rival and enemy of the Argentine ant.
The huge scale wars fought between the red fire ant and the Argentine across the south-eastern United States has prevented total Argentine dominance, pushing them back to “pockets of resistance” in places like
Austin, Texas, and Athens, Georgia. In the next thread we’ll open up the battlefronts to see how Argentine dominance has been challenged by other invasive, unicolonial ant species.