Army ants (Eciton species in South America) and driver ants (Dorylus species in Africa) have huge itinerant colonies of up to 20 million individuals, centred on a series of semi-permanent nests and satellite roost stations.
They forage in milling waves of activity, advancing on their prey (mostly insects, but also young or injured vertebrates) in broad military fronts and marching columns.
- It's a metre across and laced with tunnels and chambers – yet built entirely from a million individuals who spend their lives constantly on the move...
- "Raiding parties are the soldiers, bearing enormous heads armed with long, scissor-like mandibles capable of dismantling prey piece by piece..."
Like all ants they navigate from food source back to nest or overnight bivouac using chemical scent trails they lay on the forest floor. The heavier the traffic, the more powerfully this scent marker is reinforced. So good is this technique that workers of many species are completely blind, relying solely on smell to move around.
Why do ants get stuck in death spirals?
Sometimes a batch of many hundreds get separated from the main transport artery and double back on themselves, creating a circular path that they now follow slavishly. Unable to break free from their obligatory olfactory pursuit their blind faith impels them to run themselves to exhaustion and eventual death.
- It floats, it's larger than a dinner plate and it's made up of more than 100,000 individuals
- "As with humans, their greatest enemies are the same species. At the frontier they detect friend or foe by smell and interlopers are repulsed…"
- Kidnapped, brainwashed, enslaved: the animal that steals the young and forces them to work
