Ant colonies, real and virtual

Formica fusca

Ants, hymenoptera related to wasps, are social insects. An anthill or ant colony can contain, from a few dozen individuals, to over half a million. The number of castes varies, depending on the species, between three (fertile males and females, sterile female workers) and over twenty. The feeding a larva receives decides the caste to which it will belong.

Strange forms of parasitism have arisen among ants, as in Amazons ants (Polyergus), whose workers specialize in fighting and starve in the presence of food, unless a worker of Formica fusca feeds them. To seize these auxiliaries, the Amazons attack the nests of Formica fusca, kill their queen and enslave the workers. In extreme cases, such as ants of the Anergates genus, the queen invades a nest of Tetramorium, supplants its queen, and fed by the workers of the other species, produces eggs that become queens and males, but no workers, which are not needed.

Evolution in social insects probably reached the highest levels of instinctive complexity that can be achieved with a nervous system as limited as that of arthropods. In the tens of million years since the origin of these societies, evolution has introduced secondary changes, which have led to great diversity: there are more than three thousand species of ants, but there seems to have been no progress in their social structure. They are highly successful animals, very abundant, and spread throughout the world, but stagnant.

How insect societies arose

Solitary bee (Megachile) and social bee (Apis)

Among the insect order Hymenoptera there are many species that live independently, but there are also many others who live together in societies. Social life has evolved several times, both among ants (all of which are social) and between bees and wasps, many of which live alone. This fact should be explained: why is social life so prevalent among these insects, and how could it have evolved? In other words, did it provide any evolutionary advantage? In which way?

In insect societies, most individuals renounce reproduction and dedicate their lives to care for the queen (the only member of the society who lays eggs) and for their brothers and sisters, while they are larvae. Normally there are at least two separate castes: those who are sexually active (male and female) and those who are not (usually asexual females). The differences between active and neutral females come from the type of food they receive during their larval stage.