Ants of the genus Polyergus, of which 14 species are known, have lost the ability to care for their young or even to feed themselves. They depend upon raiding nests of ants of genus Formica, from which they abduct pupæ which are returned to the Polyergus nest and work as slaves, controlled by the pheromones of their abductors. Due to mortality of the Formica slave ants, the Polyergus colony must conduct regular raids to replenish their slave population.
Polyergus colonies reproduce by a new queen infiltrating a newly-founded Formica colony, disguising her identity with pheromones, then killing the original queen when sufficient workers have been raised to support the nascent Polyergus colony.
Does this mean that Charles Darwin endorses slavery as a normal outcome of natural selection?
Darwin considered the development of eusociality, and in particular, the existence of sterile castes in insect colonies, as “the one special difficulty, which at first appeared to me insuperable and actually fatal to my whole theory”.
It is now common to consider social insect colonies as “superorganisms” where the unit of selection is the colony, not the individual organism, just as in a multicellular organism it is the organism as a whole upon which evolution acts and not individual cells.
From this perspective, the Polyergus colony could be seen as a parasite preying upon colonies of Formica, and evolution acting upon them as it does on other parasite-host relationships.
When it comes to parasitism among the ants, Polyergus seems almost familiar compared to the Ophiocordyceps unilateralis fungus.
Applying that same logic to anthropological colonies (which we tend to refer to as “countries” or “classes”), it seems that Darwin was saying that it is totally natural for one country to prey parasitically upon another – a perfectly respectable form of the evolution of the parasite. There are good examples in the human realm, such as England’s or France’s parasitic use of forced African labor in their Carribean colonies.
How long before the Usual Suspects start pulling down statues of Charles Darwin?
My favorite regicidal ant slaver species is Monomorium santschii.
The infiltrating queen doesn’t bother killing the slave colony’s queen. She just exudes such royal presence that the slave colony’s sterile workers murder their own mother!
Well, actually, it is probably something more like spraying the victim queen with some sort of pheromone that makes her a target. There is also the phenomenon of worker ants killing off redundant queens – so that process may be the one leveraged by the slaver queen.
It is so much like what we seen in the West nowadays.